Beta thalassemia in Germany: molecular genetics and clinical phenotype in immigrant and in the native population

Dentin dysplasia, type II (MIM*125420) is an autosomal dominant disorder of dentin development. Clinically the primary dentition appears opalescent, and radiographically the pulp chambers are obliterated, resembling dentinogenesis imperfecta. However, unlike dentinogenesis imperfecta, the permanent teeth in dentin dysplasia, type II are normal in color and, on radiographs, have a thistle-tube pulp chamber configuration with pulp stones. The similarity of the primary dentition phenotype suggested that the gene for dentin dysplasia, type II is allelic with the gene for dentinogenesis imperfecta, Shields type II (DGII; MIM*125490), which has been localized to chromosome 4q13-q21. Twenty-four members of a three generation family in which ten members are affected with dentin dysplasia, type II were genotyped for microsatellite alleles specific for the area of chromosome 4q linked to DGII. Linkage was assessed by using the LINKAGE computer program, assuming autosomal dominant inheritance, a disease allele frequency of 0.0001, and complete penetrance. The maximum two-point LOD score (Zmax = 4.2 at theta = 0.0) was obtained with SPPI and D4S2691. Multipoint analysis gave a maximum LOD score of 4.33. The candidate region for dentin dysplasia, type II is approximately 14.1 cM, includes SPPI, D4S2691, D4S2690, D4S451, and D4S2456, and overlaps the most likely location of the DGII locus. A candidate gene for DGII should also be considered a candidate gene for dentin dysplasia, type II.