DiagnosisClinical Diagnosis Salih myopathy is characterized clinically by the following:Muscle weakness manifesting during the neonatal period or in early infancyDelayed motor milestones but normal cognitive developmentMuscle weakness of limb-girdle distribution, myopathic face, variable degree of ptosis, and relative calf muscle hypertrophyDevelopment of dilated cardiomyopathy between ages five and 16 yearsMajor heart rhythm disturbances leading to sudden death before age 20 yearsTestingBiochemical and electrophysiologic studiesSerum creatine kinase (CK) is marginally to moderately increased (1.5-7x normal).Electromyography (EMG) shows myopathic features (low-amplitude polyphasic potentials of short duration). Nerve conduction studies (NCS) are normal. Muscle biopsy. The following findings help distinguish Salih myopathy from congenital muscular dystrophy (CMD) and other congenital myopathies.Histology of skeletal muscle reveals a pattern compatible with congenital myopathy (Figure 1): mild variation in fiber size, abundant centrally located nuclei, no increase in connective tissue before age six years, and mild endomysial fibrosis after age six years.
Oxidative stains reveal multiple small lesions of reduced or absent oxidative activity with poorly defined boundaries.
Myofibrillar ATpase staining shows remarkable type 1 fiber predominance (>90%). In one individual massive muscle fiber loss was seen in a second biopsy taken at age ten years [Carmignac et al 2007].Immunohistochemistry of skeletal muscle shows normal expression of dystrophin, laminin α2 chain (merosin), integrin α7, α - and β-dystroglycan, desmin, emerin, and the sarcoglycans α (adhalin), β, γ, and δ.Electron microscopy of skeletal muscle (Figure 2) highlights the “minicore-like” lesions seen on histology and reveals multiple foci of sarcomere disruption and mitochondria depletion. FigureFigure 1. Skeletal muscle histology of two children with Salih myopathy taken at age four years (A and D) and 14 years (B and C).
A and D. The early biopsy shows (A) increased fiber size variability, abundant centrally located nuclei (more...)FigureFigure 2. Longitudinal electron microscopy section of skeletal muscle taken at age ten years reveals focal disruptions of sarcomeric structures (arrows), Z-disk abnormalities including focal loss of dark Z-disk material, and early dissolution of I-band (more...)Heart muscle biopsies (taken from two individuals) showed increased interstitial fibrosis compatible with dilated cardiomyopathy [Carmignac et al 2007]. Oxidative staining was normal without focal oxidative defects or significant disarray of the cardiomyocyte structure in contrast to the classic observation in hypertrophic cardiomyopathy.Electrocardiography (ECG) is very helpful in signaling the occurrence of cardiac involvement. Left axis deviation (left anterior fascicular block) can be seen as early as age four years (Figure 3). With the onset of dilated cardiomyopathy (between ages 5 and 16 years), major rhythm disturbances become evident on ECG and Holter monitoring, including polymorphic premature ventricular complexes, bigeminism and trigeminism, couplets, triplets, atrioventricular heart block, atrioventricular nodal reentrant tachycardia, premature atrial complexes, premature ventricular complexes, and ventricular tachycardia.FigureFigure 3. Electrocardiogram at age four years showing left axis deviation (left anterior fascicular block) Echocardiogram reveals, at the onset of cardiomyopathy, reduced function of the left ventricle and dilatation and global hypokinesia without wall hypertrophy. Later, dilatation involves the left atrium and ventricle, subsequently affecting all chambers leading to congestive heart failure.Radionuclide angiography using MUGA (multi-gated acquisition) scan reveals the deteriorating ventricular function with reduction of the left ventricular ejection fraction (LVEF) followed by reduction of the right ventricle ejection fraction.Respiratory function tests show a moderate restrictive pattern without clinical symptoms.Molecular Genetic Testing Gene. Salih myopathy is caused by biallelic mutation in the TTN exons (designated Mex1 and Mex3) that encode part of the C-terminal domain of titin.Note: The part of the TTN protein that spans the sarcomere M-line is encoded by six exons that have been termed Mex1-Mex6 for ‘M-line exons 1 through 6’; these correspond to the last six exons, numbers 358 to 363. Clinical testingSequence analysis of select exons. To date, biallelic mutations reported to cause Salih myopathy are small frameshift deletions in TTN exons Mex1 and Mex3 in consanguineous families of Moroccan and Sudanese origin [Carmignac et al 2007] (Table 2).Sequence analysis of other coding regions of TTN or deletion/duplication analysis is likely to increase the mutation detection frequency (see Testing Strategy).Table 1. Summary of Molecular Genetic Testing Used in Salih MyopathyView in own windowGene SymbolTest MethodMutations DetectedMutation Detection Frequency by Test Method ^{1Test AvailabilityTTNSequence analysis of select exons 2Exons Mex1 and Mex3 3~100%ClinicalSequence analysis of all 363 exons Sequence variants 4~100%Deletion / duplication analysis 5Exonic or whole-gene deletionsUnknown, none reported1. The ability of the test method used to detect a mutation that is present in the indicated gene2. Exons sequenced may vary by laboratory.3. The two mutations reported to date are in these exons; see Molecular Genetics.4. Examples of mutations detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site mutations.5. Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; included in the variety of methods that may be used are: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA) that includes this gene/chromosome segment. Interpretation of test results. For issues to consider in interpretation of sequence analysis results, click here.Information on specific allelic variants may be available in Molecular Genetics (see Table A. Genes and Databases and/or Pathologic allelic variants).Testing Strategy To confirm/establish the diagnosis in a probandClinical findings that should be present to warrant consideration of skeletal muscle biopsy and molecular genetic testing include:Delayed motor milestones but normal cognitive development;Muscle weakness of limb-girdle distribution, myopathic face, variable degree of ptosis, and relative calf muscle hypertrophy;Dilated cardiomyopathy in association with muscle weakness of limb-girdle distribution.Skeletal muscle biopsy is an integral part of the diagnostic evaluation because of the marked clinical overlap within and between congenital myopathies and congenital muscular dystrophy (CMD). Muscle biopsy sections should be examined for histology, histochemistry, immunohistochemistry, and electron microscopy. Note: Cardiac muscle biopsy is currently not indicated following the recognition of the disease.Molecular genetic testing. If clinical findings and skeletal muscle biopsy suggest Salih myopathy, perform molecular genetic testing:Perform sequence analysis of select exons (i.e., Mex1-3) first.If no mutations are identified (especially in individuals not of Moroccan or Sudanese origin), is it appropriate to sequence the other Mex exons.If only one frameshift mutation is found in Mex1-3, deletion/duplication analysis is recommended to detect a possible deletion of Mex1-6 exons.If no mutations are found in Mex1-3, sequence analysis of the entire coding region could be helpful.If no mutations have been identified by sequence analysis, deletion/duplication analysis may useful to detect a mutation (for example, homozygous deletion of several exons [e.g., Mex3-6]).Carrier testing for at-risk relatives requires prior identification of the disease-causing mutations in the family.Note: Carriers are heterozygotes for this autosomal recessive disorder and are not at risk of developing the disorder.Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutations in the family.Genetically Related (Allelic) Disorders The following are phenotypes known to be associated with mutations in TTN:Autosomal dominantHypertrophic cardiomyopathy (HCM)Dilated cardiomyopathy (DCM)Udd distal myopathyHereditary myopathy with early respiratory failure (HMERF) Autosomal recessive. Limb-girdle muscular dystrophy type 2J}

Natural History Salih myopathy is characterized by muscle weakness manifest during the neonatal period or in early infancy, and delayed motor development. Children acquire independent walking between age 20 months and four years. In the first decade of life, global motor performances are stable or tend to improve. During this period skeletal muscle involvement mainly manifests as difficulty in running, climbing stairs, and rising up from the sitting position. Those who survive childhood remain ambulant, with or without support, and maintain normal cognitive function.Moderate joint and neck contractures and spinal rigidity may start in the first decade but become more obvious in the second decade. Scoliosis develops after age 11 years.Cardiac dysfunction starts between age five and 16 years, progresses rapidly, and leads to death between ages eight and 20 years. Heart rhythm disturbances are the major cause of sudden death and their frequency and severity suggest primary involvement of the conduction system.In contrast to individuals with heterozygous mutations in TTN associated with Udd distal myopathy, the parents of individuals with Salih myopathy are heterozygous carriers of a TTN mutation and remain asymptomatic with no cardiac or muscle disorder (Figure 4). FigureFigure 4. Mid-calf muscle MRI of parents of a proband at age (A) 55 years and (B) 44 years were normal and showed no fatty degeneration of the anterior tibial muscles.

Genotype-Phenotype Correlations No genotype-phenotype correlations are known.

Differential DiagnosisFeatures of Salih myopathy distinguish it from other early-onset muscle disorders:Spinal muscular atrophy (SMA), characterized by progressive symmetric muscle weakness resulting from degeneration and loss of anterior horn cells in the spinal cord and brain stem, is a common cause of muscle weakness in the neonatal period or early infancy [Salih 2012a]. Shared features of SMA and Salih myopathy:Early onset of muscle weakness (age 6-12 months) (SMA II)Weakness resulting in frequent falling and difficulty in walking up and down stairs (SMA III)Normal intelligence Features of SMA that distinguish it from Salih myopathy:Onset after age 12 months (SMA III)Frequent finger tremblingSparing of facial musclesSerum CK: normal ECG: frequent background tremors (reflecting the spontaneous motor unit activity) but absence of cardiac involvement [Salih 2012b] EMG: neurogenic features (polyphasic waves, positive sharp waves and fibrillations) as opposed to myopathic EMG features seen in Salih myopathy. Skeletal muscle histology: group atrophy of type 1 and type 2 muscle fibers (in contrast with type 1 fiber predominance seen in Salih myopathy)Duchenne muscular dystrophy (DMD) usually manifests in early childhood with delayed milestones. Subclinical or clinical cardiac involvement presents in the majority of affected individuals. Features of DMD that distinguish it from Salih myopathy:Serum CK: high (>10-300 times normal) ECG: characteristic patternSkeletal muscle histology: established dystrophic morphology seen early in childhoodImmunohistochemical staining of skeletal muscle: negative for dystrophinSarcoglycanopathies are common in North Africa and the Arabian Peninsula, where Salih myopathy originated [Salih 2010]. Overlapping features of the sarcoglycanopathies and Salih myopathy:Onset between ages three and 15 years In some, delayed walking and frequent falling [Boyden et al 2010]Cardiomyopathy (see Limb-Girdle Muscular Dystrophy Overview)ECG: left anterior fascicular block [Subahi 2001] Features of the sarcoglycanopathies that distinguish them from Salih myopathy:Serum CK: high (10-70 times normal) ECG: tall R wave in V1 and V2 (in contrast to Salih myopathy where deep S waves are seen in the right precordial leads associated with reduced R/S ratio [Figure 3])Echocardiogram: left ventricular dysfunction associated with regional wall motion abnormalities, (e.g., inferior wall and posterior septum hypokinesia) (in contrast to Salih myopathy, in which the contractile dysfunction and dilatation, initially restricted to the left ventricle, subsequently affects all chambers [Carmignac et al 2007])Skeletal muscle histology: dystrophic early in the course of the disease Immunohistochemical staining of skeletal muscle: negative staining for one or more of the sarcoglycans α (adhalin), β, γ, and δOther forms of limb-girdle muscular dystrophy (LGMD)LGMD2I, caused by mutations in the fukutin-related protein gene (FKRP) [Nigro et al 2011], shows phenotypic overlap with Salih myopathy:Onset within the first year [Boyden et al 2010]In some, development of cardiomyopathy within the first year of life [Margeta et al 2009]Presence of muscle weakness and calf muscle hypertrophySkeletal muscle histology: in some, mild myopathic features (however, significantly reduced signal with α-dystroglycan on immunostaining)Features of LGMD2I that distinguish it from Salih myopathy:Absence of ptosisSerum CK: elevated ECG: dysmorphic notched P-waves, complete or incomplete right bundle branch block (BBB) or incomplete left BBB, and Q waves in lateral leads [Hermans et al 2010]LGMD2J, which is allelic to Salih myopathy and is caused by homozygous mutation of the C terminus of TTN, has later onset (1st to early 4th decade). In about half of all reported cases, weakness ultimately involved the distal muscles. Joint contractures have not been associated with LGMD2J [Pénisson-Besnier et al 2010] and cardiac abnormalities have not been described [Hermans et al 2010].Congenital muscular dystrophy (CMD). Muscle weakness in CMD typically begins at birth or in early infancy. Affected children present with delay or arrest of gross motor development. Subtypes of CMD known to be associated with cardiac involvement include the following:Dystroglycanopathies. Dilated cardiomyopathy has been reported in persons with mutations of FKRP and in persons with Fukuyama CMD. These disorders are distinguished from Salih myopathy by the presence of: Intellectual disability / epilepsyVariable eye malformationsBrain MRI: central nervous system malformationsLaminin α2 deficiency (also known as MDC1A) results from biallelic mutation of LAMA2 and is characterized by congenital hypotonia and delayed or arrested motor milestones, progressive diffuse joint contractures, spinal rigidity, and normal cognitive abilities in the majority of affected individuals. Approximately one third of persons with laminin α2 deficiency develop left ventricular dysfunction [Wang et al 2010]. Similarities to Salih myopathy: Myopathic facies and (in some individuals), calf muscle hypertrophy [Jones et al 2001, Quijano-Roy et al 2002] Differentiating features of laminin α2 deficiency:Brain MRI: diffuse white matter signal abnormalities Immunohistochemical staining of skeletal muscle: total or partial merosin deficiency See LAMA2-Related Muscular Dystrophy.LMNA-related CMD (L-CMD) is characterized by infantile hypotonia and weakness of axial-cervical muscles. Cardiac involvement is frequent; affected individuals develop dilated cardiomyopathy [Quijano-Roy et al 2008]. Sudden death, probably secondary to severe ventricular arrhythmia, has been reported in several individuals. L-CMD is distinguished from Salih myopathy by the absence of the following:Facial weaknessPtosisMuscle pseudohypertrophy Other congenital myopathies The congenital myopathies are characterized by hypotonia, delayed motor development, proximal weakness, poor muscle bulk, elongated myopathic facies (in many individuals), scoliosis, and foot deformities. Because of the marked clinical overlap among and between congenital myopathies and CMD, the diagnosis rests on muscle histology that shows morphologic changes resulting from disintegration of the sarcomeric Z-disk and myofibrils. Muscle biopsy findings help guide molecular genetic testing.Classic multiminicore disease (MmD) is caused by SEPN1 mutations [Ferreiro et al 2002a]. The phenotype of MmD caused by RYR1 mutations is usually milder than that caused by mutations in SEPN1, and is also associated with hand involvement [Ferreiro et al 2002b].Classic MmD has considerable overlap with Salih myopathy: Neonatal hypotonia and early-onset delayed motor developmentWeakness maximally involving the trunk and neck flexors; pelvic and shoulder girdle muscles to a lesser degreeIndividuals usually ambulatory Facial muscle weakness ranging from absent to severeSerum CK: may be slightly elevatedSkeletal muscle histology: shows common features with Salih myopathyH&E staining: variability in fiber size, increased number of internal nuclei, and normal or mildly increased fat and connective tissueMyofibrillar ATPase staining: frequently shows type 1 fiber predominance, whereas oxidative stains reveal minicores (multiple focal lesions of sarcomere disruption and/or reduced or absent oxidative activity) (see Figure 1)Electron microscopy: appearance of the cores ranging from focal areas of Z-line streaming and reduced or absent mitochondria to severe focal disorganization of myofibrillar structure [Ferreiro et al 2000] Features of MmD that distinguish it from Salih myopathy:Major respiratory involvement requiring respiratory support Cardiac involvement (right ventricular failure, cardiomyopathy) secondary to respiratory impairmentNote to clinicians: For a patient-specific ‘simultaneous consult’ related to this disorder, go to , an interactive diagnostic decision support software tool that provides differential diagnoses based on patient findings (registration or institutional access required).

ManagementEvaluations Following Initial Diagnosis To establish the extent of disease and needs of an individual diagnosed with Salih myopathy, the following are recommended:Neurologic examinationAssessment of strength and joint mobility by physical and occupational therapists Assessment of cardiac function with particular attention to possible cardiomyopathy and/or arrhythmia, which are often fatal complications Comprehensive respiratory evaluation including assessment of respiratory rate and pulmonary function Spinal x-rays to evaluate for presence of scoliosis in the second decadeMedical genetics consultationTreatment of ManifestationsTreatment involves prompt management of disease manifestations using a multidisciplinary approach that includes specialists in pediatric neurology, physiotherapy, occupational therapy, orthopedics, cardiology, and pulmonology. Stretching exercises and physical therapy help prevent contractures and promote mobility. Assistive mechanical devices including orthotics, canes, and walkers can be used as needed.Attention to education by providing school technical aid is important since cognition is normal. Stimulation and emotional support can improve school performance and the sense of social involvement.Parents and/or caregivers should be made aware of the symptoms of heart failure, arrhythmia (including presyncope and syncope), and thromboembolic disease, and of the need to urgently seek medical care when any of these symptoms appear.Training of caregivers in cardiopulmonary resuscitation may be suggested once the symptoms of cardiomyopathy start.Adequate posture should be maintained when lying prone and sitting. Garchois brace (made of plexidur, a rigid but light and heat-deformable material) is used to reduce the degree of deformity and slow the progression of scoliosis [Wang et al 2010].Cardiac transplantation should be considered for progressive dilated cardiomyopathy and heart failure refractory to medical therapy.Prevention of Secondary ComplicationsAnnual influenza vaccine and other respiratory infection-related immunizations are advised.Lower respiratory tract infections should be treated aggressively when they occur.SurveillanceMonitor as follows:Every six months: cardiac function (by ECG, 24-hour Holter-ECG recording and echocardiography) starting at age five years.Yearly: respiratory function, using pulmonary function testing or spirometry.As needed: orthopedic complications (foot deformity, joint contractures, and spinal deformity) by clinical examination and x-rays as needed.Agents/Circumstances to AvoidIbuprofen (Brufen^®):Give with care in those with evidence of cardiomyopathy. A patient who had reduced LVEF developed edema following its administration [Subahi and Salih, unpublished observation] Avoid in those with congestive heart failure.Evaluation of Relatives at RiskEarly diagnosis of at-risk sibs by clinical examination and/or molecular genetic testing is important in order to monitor motor development and cardiac function so that treatment can be instituted early.See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.Pregnancy ManagementIf a fetus is diagnosed prenatally to have Salih myopathy, special considerations are needed at and following delivery since muscle weakness may manifest during the neonatal period.Therapies Under InvestigationSearch ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions.

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. Salih Myopathy: Genes and DatabasesView in own windowGene SymbolChromosomal LocusProtein NameLocus SpecificHGMDTTN2q31​.2TitinFinnish Disease Database
ARVD/C Genetic Variants Database
TTN homepage - Leiden Muscular Dystrophy pagesTTNData 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 Salih Myopathy (View All in OMIM) View in own window 188840TITIN; TTN 611705MYOPATHY, EARLY-ONSET, WITH FATAL CARDIOMYOPATHYMolecular Genetic Pathogenesis To date, biallelic mutations reported to cause Salih myopathy are small frameshift deletions in TTN exons Mex1 and Mex3 in consanguineous families of Moroccan and Sudanese origin [Carmignac et al 2007]. Carriers of these frameshift mutations (i.e. heterozygotes) are asymptomatic, presumably as a result of nonsense-mediated decay (NMD) of the mutant mRNA. Since homozygotes survive, the NMD cannot be complete. Some titin protein that lacks the last C-terminal domains is produced. Whether the total decrease of titin protein or the loss of C-terminus is more important for the phenotype is not known.Normal allelic variants. TTN has 363 exons with a coding capacity of 113,414 bp. TTN has a large number of alternative splicing variants, which can result in confusion in exon and nucleotide numbering in the literature [Bang et al 2001, Guo et al 2010]. Transcript variant (N2A) NM_133378.4 is a long transcript with 312 exons that encodes the isoform N2A, the predominant titin isoform in skeletal muscle.Pathologic allelic variants. To date, the biallelic mutations reported to cause Salih myopathy are small frameshift deletions in TTN exons Mex1 and Mex3 in two consanguineous families of Moroccan and Sudanese origin [Carmignac et al 2007] (Table 2).Table 2. Selected TTN Pathologic Allelic VariantsView in own windowDNA Nucleotide Change
(Alias ¹) Protein Amino Acid Change
(Alias ¹)Reference Sequencesc.97820_97827delACCAAGTG
(g.289385_289392delACCAAGTG) ^{2p.Gln32608HisfX9
(p.Q33535HRfs*7) 2NM_133378​.4
NP_596869​.4c.98867delA
g.289390_289397delA
(291297delA) 2p.Lys32956Argfs*22
(Lys33883Argfs*20) 2See Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org). 1. Variant designation that does not conform to current naming conventions2. Reference sequence: AJ277892​.2Normal gene product. Titin is the biggest single polypeptide in humans, found in numerous isoform size variants. The entire coding region predicts a protein of 38,138 amino acids (4200 kd). Titin is expressed as several different isoforms, caused by alternative splicing, in different skeletal muscles and cardiac muscle [Bang et al 2001, Guo et al 2010].Titin functions as a template in sarcomere assembly and for maintenance of sarcomere integrity. The titin protein is the third myofilament in the sarcomere along with myosin and actin filaments. Titin spans more than one half the length of a sarcomere in heart and skeletal muscle. Structurally different parts of the protein perform distinct functions (mechanical, developmental, and regulatory) [Carmignac et al 2007]. Titin binds and interacts with a large number of other sarcomeric proteins.Abnormal gene product. The predicted truncated titins resulting from the frameshift mutations in Mex1 and Mex3 are incorporated into ultrastructurally normal sarcomeres in homozygous affected individuals [Carmignac et al 2007]. Therefore, absence of the last five (Mex2-Mex6) exons is compatible with life but causes this severe congenital disorder. Asymptomatic heterozygous carriers of these titin deletions presumably have sufficient full-length titin to result in normal sarcomere function.}