Amelogenesis Imperfecta Due to Mutation of the Enamelin Gene

Objective: Mutations in the human enamelin gene (ENAM) cause hypoplastic amelogenesis imperfecta (AI) through autosomal-dominant inheritance patterns, and patients may also exhibit an anterior open bite. Crown resorption of unerupted teeth occurs more frequently in patients with AI; however, this finding has not been previously associated with known ENAM mutations. This study describes the genotype-phenotype correlations for a 9y11m old boy with a homozygous ENAM mutation. Methods: A 9y11m old boy with a history of AI presented for dental treatment. Clinical and radiographic examinations were performed and genomic DNA was isolated from the saliva of the proband and his parents using the QIAamp kit (Qiagen, Santa Clara, CA). To determine the genotype, the DNA was subjected to PCR (Qiagen gel extraction kit) using primers known to amplify the ENAM gene. Treatment for the patient was completed, including extraction of two non restorable unerupted permanent molars which were preserved for evaluation by scanning electron microscopy (SEM). Results: The proband was found to be homozygous for ENAM mutation c.1258_1259insAG while the parents were both heterozygous. Clinical examination revealed that the first permanent molars were unerupted despite having complete root formation. The primary maxillary posterior teeth appeared ankylosed. There was no anterior open bite. Radiographically, the unerupted maxillary first molars appeared malformed, with resorption of a portion of the clinical crowns. SEM analysis revealed that the enamel lacked any prismatic architecture and was extremely thin. Conclusion: This study illustrates the diverse manifestations that can be associated with AI and is the first to document abnormal tooth eruption and coronal resorption with an ENAM mutation. This work was supported by NIH grants DE016079 (JTW) and DE011089 (CWG).