Hypocalcified amelogenesis imperfecta is characterized by enamel of normal thickness on newly erupted and unerupted and unresolved teeth. The enamel is soft and may be lost soon after eruption leaving the crown composed only of dentin. The enamel ... Hypocalcified amelogenesis imperfecta is characterized by enamel of normal thickness on newly erupted and unerupted and unresolved teeth. The enamel is soft and may be lost soon after eruption leaving the crown composed only of dentin. The enamel has a cheesy consistency and can be scraped from the dentin. An anterior open bite has been recorded in over 60% of the cases observed. The hypocalcification type is the most frequent type of enamel dysplasia, occurring in about 1 in 20,000 individuals (Witkop and Sauk, 1976). Large masses of supragingival calculus become deposited on the teeth, and this is frequently associated with severe gingivitis or periodontitis (Winter and Brook, 1975).
Weinmann et al. (1945) made the useful division of enamel defects into 2 classes: (1) hereditary enamel hypoplasia (see 104500), in which the enamel is hard but deficient in quantity, and (2) hereditary enamel hypocalcification, in which the ... Weinmann et al. (1945) made the useful division of enamel defects into 2 classes: (1) hereditary enamel hypoplasia (see 104500), in which the enamel is hard but deficient in quantity, and (2) hereditary enamel hypocalcification, in which the enamel is soft and undercalcified but normal in quantity and histology. Giansanti (1973) described a 17-year-old girl with hypocalcified amelogenesis imperfecta. The enamel was generally of normal thickness, but was chalky and could be penetrated or scraped off by dental instruments. The girl was also noted to have an anterior open bite. Review of her family showed autosomal dominant transmission of the condition. Mendoza et al. (2007) described a large Brazilian family with hypomineralized AI. The patients' dental enamel was creamy yellow to white and softer than normal. The enamel was easily abraded, leaving an irregular surface. Both primary and secondary teeth were affected, and there were no differences in the enamel between male and female subjects. Kim et al. (2008) described affected members of 2 Korean kindreds with hypocalcified AI. The dental enamel was of normal thickness in unerupted or newly erupted teeth, but was cheesy soft and lost soon after eruption. The teeth were very sensitive to thermal irritation. Because of rapid attrition and painful sensitivity, most of the dentitions of affected individuals were extensively restored, which precluded accurate assessment of their original condition. Several affected individuals in 1 kindred exhibited an anterior open bite, a sign that often accompanies AI regardless of type or genetic cause. Wright et al. (2009) evaluated 7 Caucasian kindreds segregating autosomal dominant hypocalcified amelogenesis imperfecta with a total of 74 affected individuals. Cephalometric analysis showed that affected individuals had an increased frequency of dental open bites and class III malocclusion (underbite). Affected individuals in 2 families had a localized phenotype in which only the enamel on the cervical one-third of the teeth was hypocalcified.
Wright et al. (2009) described the phenotypic variation in 7 Caucasian families with type III amelogenesis imperfecta due to mutations in the FAM83H gene. All of the mutations occurred in the C-terminal region and resulted in a truncated ... Wright et al. (2009) described the phenotypic variation in 7 Caucasian families with type III amelogenesis imperfecta due to mutations in the FAM83H gene. All of the mutations occurred in the C-terminal region and resulted in a truncated protein. Affected individuals with truncating mutations of 677 or fewer amino acids presented with a generalized phenotype (e.g., 611927.0007), whereas those with mutations capable of producing a protein of at least 694 amino acids (611927.0009, 611927.0010) had an attenuated, localized phenotype.
In 2 Korean families with autosomal dominant hypocalcified AI, Kim et al. (2008) identified nonsense mutations in the FAM83H gene: R325X (611927.0001) and Q398X (611927.0002). The mutations cosegregated perfectly with the disease phenotype.
In 4 families ... In 2 Korean families with autosomal dominant hypocalcified AI, Kim et al. (2008) identified nonsense mutations in the FAM83H gene: R325X (611927.0001) and Q398X (611927.0002). The mutations cosegregated perfectly with the disease phenotype. In 4 families with amelogenesis imperfecta type III previously reported by Kim et al. (2006), Lee et al. (2008) identified 4 nonsense mutations in the FAM83H gene (611927.0003-611927.0006). The mutations were all in the last exon of the gene and deleted between 503 and 883 amino acids from the C terminus of the normally 1,179-amino acid protein. Wright et al. (2009) described 6 mutations in the FAM83H gene in 7 families with autosomal dominant hypocalcified amelogenesis imperfecta. Two of the mutations (611927.0009 and 611927.0010) resulted in a milder phenotype of localized hypocalcified amelogenesis imperfecta. In affected members of 6 Turkish families segregating AI3, Hart et al. (2009) identified the same heterozygous nonsense mutation in the FAM83H gene (Q456X; 611927.0013). Based on haplotype analysis, the mutation appeared to be a founder mutation in 5 of the families and a de novo mutation in the other.