Amelogenesis imperfecta due to a mutation of the enamelin gene: clinical case with genotype-phenotype correlations

Abstract

The major protein components of the enamel matrix include the most abundant amelogenin proteins as well as less plentiful proteins such as enamelin and ameloblastin. The enamel defect in amelogenesis imperfecta (Al) generally results in enamel that is too thin (hypoplastic) or too soft (hypocalcification or hypomaturation). Previous reports indicate that mutations in the human enamelin gene (ENAM) cause hypoplastic Al through autosomal-dominant inheritance patterns and patients may also exhibit an anterior open bite. Although crown resorption of unerupted teeth occurs more frequently in Al patients, this finding has not been previously associated with known ENAM mutations. The purpose of this article was to report the genotype-phenotype correlations for a 9-year, 11-month-old boy with a homozygous ENAM mutation (c.1258_1259insAG).

Figure 1

Pedigree chart. (Males are indicated by squares, females are circles, sex unknown are diamonds, affected shaded in, and non-penetrant indicated by dark circles in the unshaded symbols. Except for the proband (indicated by arrow), affected kindred were reported by the proband's father.

Figure 2

Clinical presentation of patient (male: 9y/11m) with autosomal hypoplastic AI. Teeth are smooth and lacking proximal contacts with a generalized yellow color.

Figure 3

Panograph of patient (male: 9y/11m) with autosomal hypoplastic AI. Note the permanent molars are unerupted, with the maxillary first molars appearing externally resorbed.

Figure 4

Extracted maxillary permanent first molars with crown resorption.

Figure 5

Scanning electron micrographs of fractured teeth. A) Normal enamel surface (E) and prismatic fractured enamel layer. B) In the proband's permanent maxillary molar, the enamel lacked any prismatic architecture and was extremely thin (Line ~10 μm) (E = Enamel, D = Dentin; original magnification (1400X).

Figure 6

Chromatograms for Enam mutation (c.1258_1259insAG): A. DNA sequence of the proband, showing he is homozygous for the mutation. The AG insertion is indicated by a bracket, and generates a premature stop at codon 448. B. DNA sequence of the proband's father, who is heterozygous for the insertion, with the location indicated by an arrow.