Amelogenesis Imperfecta, Type Ic

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Retrieved

2019-09-22

Source

Omim

Trials

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Genes

ENAM, LTBP3, FAM83H, AMTN, MMP20, PEX1, WDR72, TUFT1, COL17A1, RELT, ITGB4, LAMC2, PEX26, TMEM165, KCNJ1, AMELX, AMELY, AMBN, KLK4, FAM20A, DLX3, CNNM4, LAMB3, ITGB6, STIM1, ORAI1, SLC24A4, ODAPH, ACP4, SLC10A7, ROGDI, SLC13A5, LAMA3, DNAJC21, MMP25, TP63, CKAP4, SLC24A3, FAM20C, CLDN19, CRX, CLDN16, HEXIM1, CSNK1G2, CSNK1G3, DSPP, GH1, HPX, HTN1, MSX2, NHS, COL1A2, RPGR, RPE65, UVRAG, VIS1, GPR68, CSNK1D, BMP4, ARHGAP6, ADAM10

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A number sign (#) is used with this entry because autosomal recessive local hypoplastic amelogenesis imperfecta (AI1C) is caused by homozygous mutation in the enamelin gene (ENAM; 606585) on chromosome 4q13.

Clinical Features

In the course of an extensive survey, Chosack et al. (1979) found several families with autosomal recessive local hypoplastic amelogenesis imperfecta. Characteristics included horizontal pitting and grooving more pronounced in the middle third of the crowns of most teeth of both dentitions.

In a study of 50 patients with amelogenesis imperfecta, Rowley et al. (1982) found that anterior open-bite malocclusion occurred in 24%, and was always associated with a severe discrepancy in the vertical relationship of the jaws. Vertical dysgnathia also occurred in a further 20% of the patients who did not have anterior open-bite malocclusion. Wright (1985) reported a family in which 2 sibs had autosomal recessive AI and severe anterior open bite.

Hart et al. (2003) reported 3 Turkish probands with severe generalized amelogenesis imperfecta that was both hypoplastic and radiographically unmineralized. All 3 probands also had a class II anterior open-bite malocclusion. Taurodontism was not present. All 6 parents, 3 sibs, and 3 relatives had localized, circumscribed discrete areas of enamel hypoplasia consistent with a clinical diagnosis of enamel pitting, which the authors did not consider to be a mild form of AI. Hart et al. (2003) noted that anterior open-bite malocclusion is a frequent associated finding in AI.

Molecular Genetics

In 3 patients with amelogenesis imperfecta and open-bite malocclusion, Hart et al. (2003) identified a homozygous 2-bp insertion in the ENAM gene (606585.0003). Further genotyping indicated that all 3 probands shared a common haplotype, suggesting a common ancestor. All 6 parents and family members with localized hypoplastic enamel pitting were heterozygous for the mutation. Hart et al. (2003) noted the dose-dependent effect of the 2-bp insertion mutation.