DiagnosisClinical DiagnosisThe diagnosis of junctional epidermolysis bullosa (JEB) is suspected in individuals with fragility of the skin with:Blistering with little or no trauma. Blistering may be mild or severe; however, blisters generally heal with no significant scarring. Significant oral and mucous membrane involvement Blistering may be severe and granulation tissue can form on the skin around the oral and nasal cavities, fingers and toes, and internally in the trachea. (See Figure 1, Figure 2.)FigureFigure 1. Herlitz JEB
a. Extensive widespread blistering and granulation tissue on ear
b. Hand of a child showing aplasia cutis congenital
c. Foot of an affected child
d. Exuberant perioral granulation tissue and tracheostomy (more...)FigureFigure 2. Non-Herlitz JEB
e. Minor nail dystrophy in an older child
f. Multiple blisters on the hands of an active toddler
g. Non-scarring superficial axillary erosions Because the clinical features of all types of epidermolysis bullosa (EB) overlap significantly (see Differential Diagnosis), clinical diagnosis is unreliable and examination of a skin biopsy is usually required to establish the diagnosis, especially in infants.TestingSkin biopsy. Examination of a skin biopsy by transmission electron microscopy (TEM) and/or immunofluorescent antibody/antigen mapping is the best way to reliably establish diagnosis of JEB. A punch biopsy that includes the full basement membrane zone is preferred. The biopsy should be taken from the leading edge of a fresh (<12 hours old) or mechanically induced blister and should include some normal adjacent skin. (Older blisters undergo change that may obscure the diagnostic morphology.)Note:(1) For TEM
(a) Specimens must be placed in fixation medium (such as gluteraldehyde) as designated by the laboratory performing the test.
(b) Formaldehyde-fixed samples cannot be used for electron microscopy(2) For immunofluorescent antibody/antigen mapping
(a) Specimens should be sent in sterile carrying medium (such as Michel's of Zeus) as specified by the laboratory performing the test.
(b) Some laboratories prefer flash-frozen tissue.
(c) In some laboratories the mapping only designates the level of the cleavage by using various marker antibodies of different layers of the basement membrane. A laboratory that has the antigens for the proteins of interest in EB is preferred because both the level of cleavage and the presence or absence of the specific gene products mutated in EB can be assessed.(3) Light microscopy is inadequate and unacceptable for the accurate diagnosis of EB.Transmission electron microscopy (TEM) is used to examine the number and morphology of the basement membrane zone structures — in particular, the number and morphology of anchoring fibrils, the presence of and morphology of hemidesmosomes, anchoring filaments, and keratin intermediate filaments as well as the presence of micro-vessicles showing the tissue cleavage plane. Findings on TEM include the following [Kunz et al 2000, Jonkman et al 2002, Charlesworth et al 2003, Pasmooij et al 2004a]:In all forms of JEB. Splitting in the lamina lucida of the basement membrane of the epidermis or just above the basement membrane at the level of the hemidesmosomes in the lowest level of the keratinocytes layer. In Herlitz JEB (H-JEB). Hemidesmosomes are reduced in number and hypoplastic. Anchoring filaments are markedly reduced or absent. In non-Herlitz JEB (NH-JEB). Anchoring filaments may be reduced; hemidesmosomes may be reduced or hypoplastic. Immunofluorescent antibody/antigen mapping. Findings include the following: Abnormal or absent staining with antibodies to laminin 332 (aka LAM5) [Aumailley et al 2005] resulting from mutations in LAMA3, LAMB3, or LAMC2 in Herlitz or non-Herlitz forms of JEB Abnormal or absent staining with antibodies to collagen XVII in JEB caused by mutations in COL17A1 Normal staining for other antigens (e.g., collagen VII, keratins 5 and 14) confirms the diagnosis of JEB.Note: Especially in milder forms of EB, indirect immunofluorescent studies may not be sufficient to make the diagnosis because near-normal antigen levels are detected and no cleavage plane is observed. In these cases electron microscopic examination of the skin biopsy must be performed. Alternatively, rebiopsy allowing more time (several hours) between rubbing the skin or the patient performing an activity that induces fresh blistering and blister formation prior to biopsy for IFM or EM may be required. Molecular Genetic TestingGenes. Four genes are commonly associated with the two major phenotypes of JEB, Herlitz and non-Herlitz JEB [Fine et al 1999, Anton-Lamprecht & Gedde-Dahl 2002]: Mutations in LAMB3 account for 70% of all JEB. Mutations in COL17A1 account for 12% of all JEB. Mutations in LAMC2 account for 9% of all JEB. Mutations in LAMA3 account for 9% of all JEB. Clinical testing Sequence analysis
LAMB3. Sequencing of LAMB3 detects more than 98% of LAMB3 mutations overall. Large deletions (i.e., exonic and whole-gene deletions) have been identified in LAMB3 in fewer than 1% of cases [Pulkkinen et al 1995, Cserhalmi-Friedman et al 1998, Takizawa et al 2000b, Huber et al 2002, Micheloni et al 2004, Posteraro et al 2004].
COL17A1. Sequencing of COL17A1 detects more than 98% of COL17A1 mutations overall.
LAMC2. Sequencing of LAMC2 detects more than 98% of LAMC2 mutations overall.
LAMA3. Sequencing of LAMA3 detects more than 98% of LAMA3 mutations overall.
Note: Care must be taken to sequence all of LAMA3 rather than one of the shorter isoforms.Table 1. Summary of Molecular Genetic Testing Used in Junctional Epidermolysis BullosaView in own windowGene SymbolProportion of JEB Attributed to Mutations in This Gene ¹ Test MethodMutation Detection Frequency by Gene and Test Method ^{2 , 3Test AvailabilityLAMB3 70% Sequence analysis >98% 4Clinical Deletion analysis <1% 5 Targeted mutation analysis See footnote 6 COL17A1 12% Sequence analysis >98% Clinical Deletion analysis <1% 5 LAMC2 9% Sequence analysis >98% Clinical Deletion analysis <1% 5Targeted mutation analysis See footnote 6LAMA3 9% Sequence analysis >98% 7Clinical Deletion analysis <1% 5Targeted mutation analysis See footnote 61. Varki et al [2006] 2. The ability of the test method used to detect a mutation that is present in the indicated gene3. Sequencing of all four genes results in a mutation detection frequency of 98%. Large deletions and intronic variations that alter splicing are thought to be responsible for the other 2%; however, rare mutations in ITGB4 and PLEC1 have also resulted in a JEB-like phenotype (see EB-PA) and must be taken into consideration when no mutations are identified in either of the four genes included in this table [Inoue et al 2000, Kunz et al 2000, Charlesworth et al 2003].4. Rarely, large deletions have been identified in LAMB3 which may result in a lower detection frequency [Pulkkinen et al 1995, Cserhalmi-Friedman et al 1998, Takizawa et al 2000b, Huber et al 2002, Micheloni et al 2004, Posteraro et al 2004].5. Pulkkinen et al [1997], Takizawa et al [2000b], Fassihi et al [2005], Varki et al [2006] 6. One laboratory offers targeted mutation analysis for p.Arg42*, p.Gln243*, p.Arg635*, and p.957ins77 in LAMB3; p.Arg95* mutation in LAMC2; and p.Arg650* in LAMA3 with a 45% mutation detection frequency in individuals of European ancestry. 7. Care must be taken to sequence all of LAMA3 rather than one of the shorter isoforms.Interpretation of test results. For issues to consider in interpretation of sequence analysis results, click here.Testing StrategyEstablishing the diagnosis in a proband Skin biopsy. Especially in newborns, a skin biopsy from a newly induced blister should be performed as soon as possible after initial evaluation. The skin biopsy should be studied with electron microscopy and/or indirect immunofluorescence for the basement membrane proteins to identify the affected proteins and suggest the appropriate genes to be tested. Note: Lethal forms of JEB resulting from COL17A1 mutations were recently described [Varki et al 2006, Murrell et al 2007] so the strict criteria of a lethal versus non-lethal form of JEB are not sufficient to define the order of molecular genetic testing.Molecular genetic testing. When any form of JEB is suspected, targeted mutation analysis should be the first step for individuals of the following ethnic groups: European origin: LAMB3 (p.Arg635*, p.Gln243*) Hispanic and African American: LAMB3 (c.957ins77, p.Arg42*) Pakistani: LAMA3 (p.Arg650*) [McGrath et al 1996] Italian: LAMC2 (p.Arg95*) [Posteraro et al 2004] These mutations may account for up to 45% of JEB-causing mutations.If neither or only one mutation is identified in an individual with biopsy-proven Herlitz JEB following targeted mutation analysis, sequence analysis of the four known genes has the following mutation detection frequencies [Varki et al 2006]: LAMB3: 25% LAMC2: 9% LAMA3: 10% COL17A1: 8% If neither or only one mutation is identified in an individual with biopsy-proven non-Herlitz JEB following targeted mutation analysis, sequence analysis of the four known genes has the following mutation detection frequencies [Varki et al 2006]: LAMB3: 25% COL17A1: 25% LAMC2: 3% LAMA3: 8% Carrier testing for at-risk relatives (in families with autosomal recessive inheritance) requires prior identification of the disease-causing mutations in the family. Note: Carriers are heterozygotes for an autosomal recessive disorder and are not at risk of developing the disorder.Prenatal diagnosis and preimplantation diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutation(s) in the family. Genetically Related (Allelic) DisordersLAMB3 and LAMC2. No phenotypes other than JEB are associated with mutations in LAMB3 and LAMC2. LAMA3. A related disorder, laryngoonychocutaneous (LOC or Shabbir) syndrome, or LOCS [OMIM 245660] is described in Punjabi Indians. LOCS has many phenotypic characteristics similar to NH-JEB [Figueira et al 2007, Pfendner et al 2007]. Skin fragility manifests as mild blistering and erosions of the hands and face that spreads to other parts of the body and heals with crusted lesions. Neonates may have a hoarse cry and later laryngeal abnormalities and growths, conjunctival disease, abnormal nails, and hypoplastic dental enamel. Eventually, conjunctival disease may cause blindness and laryngeal disease may cause life-threatening airway obstruction requiring tracheotomy. The LAMA3 mutation c.151insG in exon 39, one of three LAMA3 isoforms, is causative [McLean et al 2003]. Inheritance is autosomal recessive.Diagnosis of LOCS may be complicated by the lack of a definitive cleavage plane on TEM and reduced but not absent laminin 5 staining by immunofluorescence for the basement membrane proteins. Sequence analysis of all 76 exons of LAMA3, which encodes all three isoforms, is necessary to provide definitive diagnosis, especially in neonates.COL17A1. Mutations in COL17A1 may also be associated with an epidermal keratinocyte cleavage plane usually associated with epidermolysis bullosa simplex (EBS) [Pasmooij et al 2004a].}

Natural HistoryBefore the molecular basis of junctional epidermolysis bullosa (JEB) was understood, subtypes were identified (see Nomenclature) based primarily on clinical features, mode of inheritance, and the presence or absence of laminin 5 and anchoring filaments on skin biopsy. Broad classification of JEB includes H-JEB (aka lethal) and NH-JEB (aka non-lethal) and is based on severity and survival past the first years of life [Fine et al 1999, Pulkkinen & Uitto 1999, Irvine & McLean 2003, Uitto & Richard 2005].Herlitz JEB (H-JEB). In this classic severe form of JEB, blisters are present at birth or become apparent in the neonatal period. Blistering is very severe and may lead to large regions of affected skin with significant granulation tissue. Granulation tissue characteristically appears around the nose, mouth, ears, and tips of the fingers and toes as well as in areas subject to friction such as the buttocks and the back of the head. Persistent plaques on the face can be challenging to treat. The granulation tissue manifests as large eroded patches and plaques that are friable and bleed easily and profusely. There can be extensive loss of blood, fluid, and protein. Such erosions are often life threatening because they make these infants susceptible to electrolyte imbalance and infection including sepsis and sudden death. If the infant survives, blistering may continue throughout life, generally without scarring unless there has been severe secondary infection. Scarring pseudosyndactyly of the hands and feet fusing the digits into "mitten" hands and feet with severe loss of function has been seen in a few individuals with H-JEB who survive [Fine et al 1999].In addition to cutaneous involvement, mucosal involvement of the mouth, upper respiratory tract, esophagus, bladder, urethra, and corneas can be seen. Accumulation of granulation tissue surrounding the airway is usually subglottic and the first manifestation is a weak, hoarse cry. Eventually, compression and obstruction of the airway result in stridor and respiratory distress. Unless tracheostomy is performed, many children succumb from respiratory complications. However, managing a tracheostomy in a child with such fragile skin is difficult.Bladder and urethral epithelial involvement can cause dysuria, urinary retention, urinary tract infections, and eventual renal compromise. Renal and ureteral anomalies that can be seen include dysplastic/multicystic kidney, hydronephrosis/hydroureter, acute renal tubular necrosis, obstructive uropathy, ureterocele, duplicated renal collecting system, and absent bladder [Puvabanditsin et al 1997, Kambham et al 2000, Nakano et al 2000, Wallerstein et al 2000, Fine et al 2004, Varki et al 2006, Pfendner et al 2007].Esophageal narrowing has been reported, but is less common than in children with recessive dystrophic EB (RDEB).Secondary complications common in H-JEB include the following:Growth retardation from malnutrition as a result of poor intake and an increased nutritional demand for tissue healing Anemia Alopecia Cutaneous infection Sepsis Electrolyte imbalance Osteoporosis [Fewtrell et al 2006] Squamous cell carcinoma [Mallipeddi et al 2004] Enamel dysplasia with pitting of the teeth [Kirkham et al 2000, Nakamura et al 2006] Most children with H-JEB do not survive past the first year of life.Non-Herlitz JEB (NH-JEB). A spectrum of JEB clinical phenotypes, all of which are less severe than classic H-JEB, comprises NH-JEB. The phenotype may be mild with blistering localized to hands, feet, knees, and elbows with or without renal, ureteral, or esophageal involvement or relatively more widespread including flexural areas and trunk. Some children virtually never blister after the newborn period. The severe granulation tissue and respiratory compromise of H-JEB are rare.Varying degrees of alopecia and onychodystrophy as well as tooth pitting remain hallmarks of this type of JEB.Manifestations that can occur in H-JEB, NH-JEB, and EB with pyloric atresia (EB-PA) as well as dystrophic epidermolysis bullosa (DEB) and epidermolysis bullosa simplex (EBS). The following manifestations are now recognized to be found in the major EB types as described in the findings of the National EB Registry [Fine et al 1999]: Congenital localized absence of skin (aplasia cutis congenita) can be seen in any of the major types of EB and is not a discriminating diagnostic feature of any of these types of EB in general or any subtype of JEB. Congenital absence of skin on the extremities had been classified as Bart syndrome [OMIM 132000] but currently is considered a manifestation of all types of EB. Milia are small white-topped papules; they are often confused with epidermal cysts and are not confined to any type of EB, although they are most common in individuals with DEB. Nail dystrophy is defined as changes in size, color, shape, or texture of nails and is not confined to any one form of EB. Scarring alopecia is defined as complete loss of scalp hair follicles as a result of scarring and loss of hair follicles. Scarring alopecia is more prevalent in JEB and DEB but is not confined solely to any one form of EB. Hypotrichosis is defined as reduction in the number of hair follicles in a given area compared to the number of hair follicles in the same area of a normal individual of the same gender. Hypotrichosis is not confined to any one form of EB. Pseudosyndactyly and other contractures. Pseudosyndactyly is defined as the partial or complete loss of web spaces between any digits of the hands or feet. "Other contractures" refers to loss of mobility of any other joints as a result of fibrous tissue scars. Although these changes are more prevalent in DEB, they have also been observed occasionally in the other forms of EB. Scarring is not confined to any form of EB and has been observed in 30% of those with EBS, 76% of those with JEB, and up to 98% of those with DEB. Exuberant granulation tissue, previously thought to be confined to those with JEB (23%), has now been observed in a small percentage of those with DEB (≤12%) and EBS (0.7%). This finding is misleading because it does not usually appear until the affected child is a few years old and most children with H-JEB do not survive that long.

Genotype-Phenotype CorrelationsH-JEB. The severest forms of H-JEB are a result of inactivating mutations on both alleles, which result in little or no functional protein [Varki et al 2006]. For frameshift mutations, the severity may be related to the position of the stop codon; however, the presence of some functional protein seems to be the most important factor in ameliorating disease severity. Less severe forms of H-JEB generally result from other amino acid substitutions and splice-junction mutations, although it is difficult to generalize because of the wide phenotypic variability and range of mutations that has been identified [Varki et al 2006]. In addition, moderation of phenotypes expected to be severe has occurred through in-frame skipping of exons containing nonsense or frameshift mutations [McGrath et al 1999].

Differential DiagnosisThe four major types of EB, caused by mutations in ten different genes, are EBS, hemidesmosomal EB, junctional epidermolysis bullosa (JEB), and DEB (Figure 3). Although agreement exists as to diagnostic criteria for some types of EB, the validity of rarer subtypes and their diagnostic criteria are disputed. Excellent clinical reviews are the chapter on EB in Principles and Practice of Medical Genetics [Anton-Lamprecht & Gedde-Dahl 2002] and Fine's Revised Classification System [Fine et al 1999, Fine et al 2000]. FigureFigure 3. Diagram showing locations affected by mutations causing the four major subtypes of EB syndromes The four major types of EB share fragility of the skin, manifested by blistering with little or no trauma. A positive Nikolsky sign (blistering of uninvolved skin after rubbing) is common to all types of EB. No clinical findings are specific to a given type; thus, establishing the type of EB type requires a fresh skin biopsy from a newly induced blister that is stained by indirect immunofluorescence for critical basement membrane protein components. The diagnosis is established by determining the cleavage plane on TEM and the presence/absence of these protein components by immunofluorescent antibody/antigen mapping and their distribution. Electron microscopy is also diagnostic and often more useful in milder forms of EB.Clinical examination is useful in determining the extent of blistering, the presence of oral and other mucous membrane lesions, and the presence and extent of scarring.Limitations of the clinical findings in establishing the type of EB include the following:In young children and neonates the extent and severity of blistering and scarring may not be established or significant enough to allow identification of EB type. Mucosal and nail involvement and the presence or absence of milia may not be helpful discriminators (see Clinical Description). Post-inflammatory changes such as those seen in EBS, Dowling-Meara type (EBS-DM) are often mistaken for scarring or mottled pigmentation. Scarring can occur in EBS and JEB as a result of infection of erosions or scratching, which further damages the exposed surface. Congenital absence of the skin can be seen in any of the three major types of EB (i.e., EBS, JEB, DEB) and is not a discriminating diagnostic feature (see Clinical Description). Clinical findings that tend to be characteristic for a specific type of EB include the following:Corneal erosions, esophageal strictures, and nail involvement may indicate DEB. Scarring limited to the hands and feet in milder cases suggests autosomal dominant DEB (DDEB). Pseudosyndactyly (mitten deformities) and contractures in older children and adults usually suggests autosomal recessive DEB (RDEB). Hoarseness and respiratory distress suggest H-JEB. Granulation tissue suggests JEB. Hyperkeratosis of the palms and soles suggests EBS, especially the DM type. Epidermolysis bullosa simplex (EBS) is characterized by fragility of the skin that results in nonscarring blisters caused by little or no trauma. Four clinical subtypes of EBS range from relatively mild blistering of the hands and feet to more generalized blistering, which can be fatal. In EBS, Weber-Cockayne type (EBS-WC), blisters are rarely present at birth and may occur on the knees and shins with crawling or on the feet at approximately age 18 months; some individuals manifest the disease in adolescence or early adulthood. Blisters are usually confined to the hands and feet, but can occur anywhere if trauma is significant. In EBS, Koebner type (EBS-K), blisters may be present at birth or develop within the first few months of life. Involvement is more widespread than in EBS-WC, but generally milder than in EBS-DM. In EBS with mottled pigmentation type (EBS-MP), skin fragility is evident at birth and clinically indistinguishable from EBS-DM; over time, progressive brown pigmentation interspersed with depigmented spots develops on the trunk and extremities, the pigmentation disappearing in adult life. Focal palmar and plantar hyperkeratoses may occur. In EBS, Dowling-Meara type (EBS-DM), onset is usually at birth; severity varies greatly, both within and among families. Widespread and severe blistering and/or multiple grouped clumps of small blisters are typical and hemorrhagic blisters are common. Improvement occurs during mid to late childhood. EBS-DM appears to improve with warmth in some individuals. Progressive hyperkeratosis of the palms and soles begins in childhood and may be the major complaint of affected individuals in adult life. Nail dystrophy and milia are common. Both hyperpigmentation and hypopigmentation can occur. Mucosal involvement in EBS-DM may interfere with feeding. Blistering can be severe enough to result in neonatal or infant death. Hemidesmosomal EB. Pulkkinen & Uitto [1999] proposed that EB with muscular dystrophy (EB-MD) and EB with pyloric atresia (EB-PA) be considered "hemidesmosomal JEB" because the involved proteins are located in the hemidesmosomes. Within basal keratinocytes, plectin is localized to the inner plaques of the hemidesmosomes, which are hypoplastic and show poor association with keratin filaments. Electron microscopy of skin biopsies reveals a plane of cleavage (level of separation) within the bottom layer of the basal keratinocytes, just above the hemidesmosomes. (See EB-PA.) Note: "Hemidesmosomal epidermolysis bullosa" is not a universally accepted designation; the following three types typically have been included either with EBS or JEB:EB-MD [OMIM 226670]. Approximately 50 cases of EB-MD have been reported worldwide. Some persons with EB as a result of PLEC1 mutations develop muscular dystrophy [Smith et al 1996, Charlesworth et al 2003, Koss-Harnes et al 2004, Schara et al 2004, Pfendner et al 2005]. Blistering occurs early and is generally mild. Muscular dystrophy may not appear until later childhood, adolescence, or in some cases adulthood, and can cause immobility and eventually death later in life. Mutations have been described throughout PLEC1 but seem to cluster in the two long open reading frames containing exons in the 3' end of the gene. Nonsense, missense, insertion/deletion, and splice-junction mutations have been described. The mildest phenotypes are usually associated with in-frame insertions or deletions, which do not alter the reading frame of the microRNA (mRNA) [Pfendner et al 2005]. Inheritance is autosomal recessive.
A single lethal case of autosomal recessive EBS as a result of PLEC1 mutations has also been described [Charlesworth et al 2003]. Kunz et al [2000] also described a case of EBS with severe mucous membrane involvement as a result of mutations in PLEC1. EB-PA. In several US and Japanese families, EB with pyloric atresia is associated with premature termination mutations in PLEC1 [Nakamura et al 2005, Pfendner & Uitto 2005], and more commonly, the gene encoding β4 integrin (ITGB4). Rare cases of EB-PA are associated with mutations in the α6 integrin gene (ITGA6). Although disease course is severe and often lethal in the neonatal period, non-lethal forms have been described. Individuals with mutations in the genes encoding α6 or β4 integrin may also show renal and ureteral anomalies, including dysplastic/multicystic kidney, hydronephrosis/hydroureter, acute renal tubular necrosis, obstructive uropathy, ureterocele, duplicated renal collecting system, and absent bladder [Puvabanditsin et al 1997, Kambham et al 2000, Nakano et al 2000, Wallerstein et al 2000, Varki et al 2006, Pfendner et al 2007]. Occasionally, pyloric atresia may be suspected during gestation as a result of oligohydramnios, with or without elevated alpha-fetoprotein and acetylcholinesterase levels, and echogenic material in the amniotic fluid [Dolan et al 1993, Azarian et al 2006]. EBS-Ogna [OMIM 131950], observed in one Norwegian and one German family, is a result of the site-specific autosomal dominant missense p.Arg2110Trp mutation within the rod domain of PLEC1 [Koss-Harnes et al 2002]. A single lethal case of autosomal recessive EBS resulting from PLEC1 mutations has also been described [Charlesworth et al 2003]. Kunz et al [2000] also described a case of EBS with severe mucous membrane involvement as a result of mutations in PLEC1. Dystrophic EB (DEB). The blister forms below the basement membrane, and the basement membrane is attached to the blister roof, resulting in scarring when blisters heal. Mutations in COL7A1, the gene encoding type VII collagen, have been demonstrated in all forms of DEB, both dominant and recessive [Varki et al 2007].

ManagementEvaluations Following Initial DiagnosisTo establish the extent of disease in an individual diagnosed with junctional epidermolysis bullosa (JEB), the following evaluations are recommended:Evaluation of the sites of blister formation, including mouth, esophagus, and airway in a child with progressive hoarseness or stridor Direct examination of the airway by an experienced otolaryngologist with appropriately small and lubricated instruments to determine the extent of airway compromise so that decisions regarding tracheostomy can be discussed with the family Measurements of hemoglobin and electrolytes to evaluate for anemia and electrolyte imbalance Skin bacterial cultures and blood cultures in clinically ill infants to decide appropriate antibiotic treatment Treatment of ManifestationsSkin. The skin needs to be protected from shearing forces and caretakers need to learn how to handle the child with EB. New blisters should be lanced and drained to prevent further spread from fluid pressure. In most cases, dressings for blisters involve three layers:A primary nonadherent dressing that does not strip the top layers of the epidermis. Tolerance to different primary layers varies. Primary layers include the following: Ordinary Band-Aids^® Dressings impregnated with an emollient such as petrolatum or topical antiseptic (e.g., Vaseline^® gauze, Adaptic^®, Xeroform^®) Nonstick products (e.g., Telfa^®, N-terface^®) Silicone-based products without adhesive (e.g., Mepitel^®, Mepilex^®) A secondary layer that provides stability for the primary layer and adds padding to allow more activity. Rolls of gauze (e.g., Kerlix^®) are commonly used. A tertiary layer that usually has some elastic properties and ensures the integrity of the dressing (e.g., Coban^® or elasticized tube gauze of varying diameters such as Band Net^®) Other. The most common secondary complication is infection. In addition to wound care, treatment of chronic infection of wounds is a challenge. Many affected individuals become infected with resistant bacteria, most often methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Both antibiotics and antiseptics need to be employed. Esophageal strictures and webs can be dilated repeatedly to improve swallowing [Azizkhan et al 2007].A hoarse cry in an infant should alert to the possibility of airway obstruction with granulation tissue. Decisions about tracheostomy should involve the family and take into consideration the medical condition of the infant. Because of the poor prognosis and severe pain and discomfort experienced by these infants, a discussion with the family and hospital ethics committee often helps to determine the type of intervention and comfort care to provide [Yan et al 2007].Some children have delays or difficulty walking because of blistering and hyperkeratosis. Appropriate footwear and physical therapy are essential to preserve ambulation.Psychosocial support, including social services and psychological counseling, is essential [Lucky et al 2007].Dental care is necessary because of inherent enamel abnormalities [Kirkham et al 2000].Prevention of Secondary ComplicationsFluid and electrolyte problems, which can be significant and even life-threatening in the neonatal period and in infants with widespread disease, require careful management.In infants and children with JEB with more severe involvement, failure to thrive may be a problem, requiring additional nutritional support including a feeding gastrostomy when necessary to assure adequate caloric intake [Haynes 2006].In children who survive the newborn period, nutritional deficiencies must also be addressed when they are identified:Calcium and vitamin D replacement for osteopenia and osteoporosis Zinc supplementation for wound healing [Mellerio et al 2007] Iron-deficiency anemia, a chronic problem, can be treated with oral or intravenous iron infusions and red blood cell transfusions.SurveillanceScreening for iron-deficiency anemia should be routine with complete blood counts and measurement of serum iron concentration to provide iron supplementation when necessary.Screening for zinc deficiency by measuring serum zinc concentration should be routine to provide zinc supplementation when necessary to enhance wound healing.Screening with bone mineral density scanning may pick up early osteopenia and/ or osteoporosis. No guidelines have been established regarding the age at which this should begin.Because of the risk for squamous cell carcinoma, surveillance in the second decade of life for wounds that do not heal, have exuberant scar tissue, or otherwise look abnormal is essential. Frequent biopsies of suspicious lesions followed by local excision may be necessary.Agents/Circumstances to AvoidMost persons with JEB cannot use ordinary medical tape or Band-Aids^®.Poorly fitting or coarse-textured clothing and footwear should be avoided as they can cause trauma.Activities that, in general, traumatize the skin (e.g., hiking, mountain biking, contact sports) should be avoided; affected individuals who are determined to participate in such activities should be encouraged to find creative ways to protect their skin.Evaluation of Relatives at RiskSee Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.Therapies Under InvestigationSeveral approaches to gene therapy for JEB have been proposed focused on retroviral modification of in vitro epidermal cells [Robbins et al 2001, Ortiz-Urda et al 2003]. One successful clinical trial has been conducted using transplantation of sheets of genetically modified epidermal stem cells in a patient with LAMB3 mutations [Mavilio et al 2006]. Animal models include intra-amniotic prenatal laminin 332 delivery in the mouse [Muhle et al 2006] and a spontaneous form of JEB in the dog [Capt et al 2005, Spirito et al 2006].The knockout mouse model for all JEB-related genes should facilitate the development of these therapeutic approaches [Jiang & Uitto 2005].Search ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions.OtherCesarean section is often recommended to reduce trauma to the skin of an affected fetus during delivery.

Molecular GeneticsInformation in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.Table A. Junctional Epidermolysis Bullosa: Genes and DatabasesView in own windowGene SymbolChromosomal LocusProtein NameLocus SpecificHGMDLAMA318q11​.2Laminin subunit alpha-3LAMA3 homepage - Mendelian genesLAMA3LAMC21q25​.3Laminin subunit gamma-2LAMC2 homepage - Mendelian genesLAMC2COL17A110q24​.3-q25.1Collagen alpha-1(XVII) chainCOL17A1 @ LOVDCOL17A1LAMB31q32​.2Laminin subunit beta-3LAMB3 homepage - Mendelian genesLAMB3Data are compiled from the following standard references: gene symbol from HGNC; chromosomal locus, locus name, critical region, complementation group from OMIM; protein name from UniProt. For a description of databases (Locus Specific, HGMD) to which links are provided, click here.Table B. OMIM Entries for Junctional Epidermolysis Bullosa (View All in OMIM) View in own window 113811COLLAGEN, TYPE XVII, ALPHA-1; COL17A1 150292LAMININ, GAMMA-2; LAMC2 150310LAMININ, BETA-3; LAMB3 226650EPIDERMOLYSIS BULLOSA, JUNCTIONAL, NON-HERLITZ TYPE 226700EPIDERMOLYSIS BULLOSA, JUNCTIONAL, HERLITZ TYPE 600805LAMININ, ALPHA-3; LAMA3Molecular Genetic PathogenesisThe proteins encoded by LAMA3, LAMB3, and LAMC2 assemble into the laminin 332 heterotrimer (aka LAM5 [Aumailley et al 2005]). A mutation in these genes can lead to reduced resistance to minor trauma and the resulting muco-cutaneous blistering that is the hallmark of junctional epidermolysis bullosa (JEB). The type of mutation, the biochemical properties of the substituted amino acid, if present, and its location determine the severity of the blistering phenotype (see Genotype-Phenotype Correlations). Nonsense mutations predominate in the severe forms of JEB and result in the absence of one of the three proteins that assemble into laminin 332. Missense mutations in key positions of the protein subunits affect the ability of the laminin α3 β3 and γ2 polypeptides to assemble into a trimeric molecule, its secondary structure, and its ability to form the intracellular anchoring fibrils of the lamina densa.Collagen XVII forms an integral part of the hemidesmosome and has an intracellular as well as extracellular component. There is evidence that it interacts with alpha-6 integrin within the hemidesmosome. The hemidesmosomes, structures made up of several protein components including COLXVII, alpha-6 beta-4 integrin, BPAG1, and plectin, anchor the epidermal cells to the underlying dermis. The type and position of mutations in COL17A1 determine whether some partially functional protein is made and also affect the level of the cleavage plane of the skin. In some cases, mutations affecting the intracellular domain result in a cleavage plane within the lowest level of the basal keratinocytes usually associated with EBS [Charlesworth et al 2003]. LAMA3 Normal allelic variants. All of LAMA3 is encoded in 76 exons spanning 318 kb on chromosome 18q11.2. There are three isoforms (LAMA3a, LAMA3b1, and LAMA3b2) produced by alternative splicing (see Normal gene product). Pathologic allelic variants. Nonsense, missense, splicing, and insertion deletion mutations have been reported [Varki et al 2006, Nakano et al 2002a]. Premature termination codon mutations on both alleles result in the severe (Herlitz) form of JEB in most instances. A few mildly affected individuals with JEB with premature termination codon mutations have been reported [Nakano et al 2002a]. Amino acid substitutions and splicing mutations may result in a milder phenotype [Posteraro et al 1998, Nakano et al 2002a]. The common hot spot mutations are reportedly present in approximately 45% of H-JEB cases in the US (see Testing Strategy). These mutations invariably result in premature termination codons and when found on both alleles result in H-JEB. Overlapping phenotypes may exist in which mutations in LAMA3 result in skin fragility with eye and laryngeal involvement [Varki et al 2006, Figueira et al 2007].Table 2. Selected LAMA3 Pathologic Allelic VariantsView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencesc.151insGp.Val51Glyfs*3AY327114​.1
AAQ72569​.1 c.1948A>Tp.Arg650*See Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org).Normal gene product. There are three isoforms (LAMA3a, LAMA3b1, and LAMA3b2) produced by alternative splicing. Of the two LAMA3b isoforms, LAMA3b1 encodes a longer protein of 3,333 amino acids in 75 exons (exons 1-38 and 40-76 of the gene); the shorter isoform LAMA3b2 encodes a protein of 3289 amino acids in 74 exons (exons 1-9, 11-38, and 40-76 of the gene) and differs from LAMA3b1 in that exon 10 is removed by alternative splicing. The shorter LAMA3a isoform of 1724 amino acids is encoded in 38 exons (exons 39-76 of LAMA3) and is unique in that exon 39 is expressed. The laminin A3 protein associates with laminin B3 and C2 proteins to form the laminin 332 heterotrimer that comprises the anchoring fibrils in the epidermis. The anchoring fibrils hold the layers of the basal lamina together and form associations with collagen VII on the dermal side and plectin and α6 β4 integrin in the hemidesmosomes on the epidermal side. This interaction allows the formation of the protein network of the epidermis, which results in a flexible and resilient barrier to resist trauma.Abnormal gene product. See Molecular Genetic Pathogenesis. In all three genes (LAMB3, LAMC2, and LAMA3), amino acid substitutions, splicing mutations, and in-frame deletions and insertions may result in the formation of some partially functional protein that results in a milder phenotype. Specific amino acid substitutions, such as replacement of cysteine residues, inhibit the formation of disulfide bonds, result in altered laminin 332 intra- and intermolecular associations, and may result in a more severe phenotype. Usually, on a skin biopsy studied with immunofluorescence, if synthesis of one of the proteins is disrupted, the staining for the other two proteins will also be affected. LAMB3 Normal allelic variants. The normal LAMB3 cDNA has an open reading frame of 3516 nucleotides in 23 exons spanning 29 kb. Pathologic allelic variants. Nonsense, missense, splicing, and insertion deletion mutations have been reported [Nakano et al 2002b, Varki et al 2006]. A few cases of mildly affected JEB patients with premature termination codon mutations have been reported [Pulkkinen et al 1998, Nakano et al 2002a]. Amino acid substitutions and splicing mutations may result in a milder phenotype [Mellerio et al 1998, Posteraro et al 1998, Nakano et al 2002a].Table 3. Selected LAMB3 Pathologic Allelic VariantsView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencesc.124C>Tp.Arg42*NM_000228​.2
NP_000219​.2 c.727C>Tp.Gln243*c.957ins77p.Glu320*c.1903C>Tp.Arg635*See Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org).Normal gene product. The laminin B3 protein has 1,172 amino acids. It associates with laminin A3 and C2 proteins to form the laminin 332 heterotrimer that comprises the anchoring fibrils in the epidermis. Abnormal gene product. See Molecular Genetic Pathogenesis. In all three genes (LAMB3, LAMC2, and LAMA3), amino acid substitutions, splicing mutations, and in-frame deletions and insertions may result in the formation of some partially functional protein that results in a milder phenotype. Specific amino acid substitutions, such as replacement of cysteine residues, inhibit the formation of disulfide bonds, result in altered laminin 332 intra- and intermolecular associations, and may result in a more severe phenotype. Usually, on a skin biopsy studied with immunofluorescence, if synthesis of one of the proteins is disrupted, the staining for the other two proteins will also be affected. Reversion by LAMB3 mosaicism to a normal phenotype has been described and has implications for treatment [Pasmooij et al 2007]. LAMC2 Normal allelic variants. Two protein isoforms are encoded by LAMC2. The longest is encoded in 23 exons and is expressed in the epidermis. The shorter isoform produced by alternative splicing ends two codons past exon 22 and is expressed in the cerebral cortex, lung, and distal tubules of the kidney. The epidermal LAMC2 cDNA has an open reading frame of 3573 nucleotides encoding 1191 amino acids in 23 exons spanning 55 kb. Pathologic allelic variants. Nonsense, missense, splicing, and insertion deletion mutations have been reported [Castiglia et al 2001, Nakano et al 2002b; Varki et al 2006]. Amino acid substitutions and splicing mutations may result in a milder phenotype [Posteraro et al 1998, Castiglia et al 2001, Nakano et al 2002a].Table 4. Selected LAMC2 Pathologic Allelic VariantsView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencesc.283C>Tp.Arg95*NM_005562​.2
NP_005553​.2 See Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org).Normal gene product. The laminin C2 protein associates with laminins A3 and C2 to form the laminin 332 heterotrimer that makes up the anchoring fibrils in the epidermis. Abnormal gene product. See Molecular Genetic Pathogenesis. In all three genes (LAMB3, LAMC2, and LAMA3), amino acid substitutions, splicing mutations, and in-frame deletions and insertions may result in the formation of some partially functional protein that results in a milder phenotype. Specific amino acid substitutions, such as replacement of cysteine residues, inhibit the formation of disulfide bonds, result in altered laminin 332 intra- and intermolecular associations, and may result in a more severe phenotype. Usually, on a skin biopsy studied with immunofluorescence, if synthesis of one of the proteins is disrupted, the staining for the other two proteins will also be affected. COL17A1 Normal allelic variants. The cDNA has an open reading frame of 5610 nucleotides encoding 1497 amino acids in 56 exons. There is one alternatively spliced mRNA variant [Ruzzi et al 2001]. Pathologic allelic variants. Mutations in COL17A1, which encodes the collagen XVII protein, a component of the hemidesmosome, result in typically less severe forms of JEB (non-Herlitz) [Gatalica et al 1997, Pulkkinen et al 1999, Takizawa et al 2000a, van Leusden et al 2001, Pasmooij et al 2004b], although a few cases of lethal JEB resulting from COL17A1 mutations have been reported [Varki et al 2006, Murrell et al 2007]. All types of mutations, including premature termination codon, nonsense, insertion/deletion, splice junction, and missense, distributed throughout the gene have been described. The type and location of the mutations and the response of the cells to the mutations determines the phenotype, which can range from mild to severe and in some cases lethal. Reversion to a normal phenotype has been described [Pasmooij et al 2005]. Normal gene product. Collagen XVII (also known as BP180) is composed of intracellular and extracellular domains separated by a transmembrane domain that distinguishes collagen XVII from other collagen family members. The intracellular domain is localized within the basal keratinocyte; the ectodomain is localized outside the cell and serves as an association point with other components of the basement membrane zone. The carboxy-terminal half of collagen XVII, a stretch of 916 amino acids, consists of 15 collagen domains of variable length (15 to 242 amino acids) that are separated by short stretches of non-collagen sequences. The collagenous domains associate to form a homotrimeric triple helical segment of the molecule characteristic of all collagen family members. Abnormal gene product. Premature termination codon mutations that result in a null allele cause skin fragility, dental abnormalities, and alopecia usually found in patients with NH-JEB. Other mutations may result in varying phenotypic severity. Although COL17A1 mutations do not usually result in lethality, several cases of a neonatal lethal phenotype were recently described [Varki et al 2006, Murrell et al 2007]. Mutations that affect the intracellular domain may result in a cleavage plane more consistent with EBS and be misleading in terms of diagnosis based on electron microscopy biopsy results. Mutations that affect the transmembrane domain may result in intracellular accumulation of collagen XVII protein. Although glycine substitutions in COL17A1 have been described, no autosomal dominant mutations resulting in skin fragility have been identified. Heterozygote carriers of a glycine substitution [Nakamura et al 2006] or other COL17A1 mutations [Murrell et al 2007] may exhibit dental enamel pitting and this characteristic may be diagnostic for COL17A1 mutations in a family with an affected child [Murrell et al 2007].