Autosomal recessive amelogenesis imperfecta pigmented hypomaturation type is characterized by enamel of normal thickness that is hypomineralized and has a mottled appearance. The slightly soft enamel detaches easily from the dentin, and radiographs show a lack of contrast ... Autosomal recessive amelogenesis imperfecta pigmented hypomaturation type is characterized by enamel of normal thickness that is hypomineralized and has a mottled appearance. The slightly soft enamel detaches easily from the dentin, and radiographs show a lack of contrast between enamel and dentin (Witkop, 1989).
Kim et al. (2005) reported a family in which 2 members had autosomal recessive pigmented hypomaturation AI. The enamel layer of the teeth was pigmented, showing an agar brown discoloration. The surface of the enamel was mottled and ... Kim et al. (2005) reported a family in which 2 members had autosomal recessive pigmented hypomaturation AI. The enamel layer of the teeth was pigmented, showing an agar brown discoloration. The surface of the enamel was mottled and rough, but hard and brittle. Chunks of enamel had fractured away from several teeth. Radiographically, the enamel layer was usually more opaque then the underlying dentin, but not in all areas, and was never as radioopaque as normal enamel. The proband had an anterior open bite. - Comparison of AI2A1 and AI2A2 Kim et al. (2005) compared the dental phenotypes of the KLK4 (Hart et al., 2004) and MMP20 (their study) probands and noted many similar features. The enamel crowns are normal in size and shape, have a rougher, duller, less reflective surface than normal enamel, appear to be more brittle in that they show a tendency to fracture or chip, but do not appear to be particularly susceptible to dental caries. The radiodensity of the defective enamel is generally less than that of normal enamel, but can still be distinguished from the underlying dentin on radiographs. The coloration of the teeth is different, but extrinsic staining since tooth eruption could have contributed to the current appearance. The KLK4 teeth have a more homogeneous dark yellow hue, while the MMP20 teeth have an irregular grayish brown discoloration and are a little more glossy. Overall, the dental phenotypes in the KLK4 and MMP20 probands are remarkably similar.
In both affected members of a family segregating pigmented hypomaturation AI, Kim et al. (2005) identified homozygosity for a splice site mutation in the MMP20 gene (604629.0001).