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Brachydactyly Type B: Linkage to Chromosome 9q22 and Evidence for Genetic Heterogeneity

Lookup NU author(s): Professor John LoughlinORCiD


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Brachydactyly type B (BDB), an autosomal dominant disorder, is the most severe of the brachydactylies and is characterized by hypoplasia or absence of the terminal portions of the index to little fingers, usually with absence of the nails. The thumbs may be of normal length but are often flattened and occasionally are bifid. The feet are similarly but less severely affected. We have performed a genomewide linkage analysis of three families with BDB, two English and one Portugese. The two English families show linkage to the same region on chromosome 9 (combined multipoint maximum LOD score 8.69 with marker D9S257). The 16-cM disease interval is defined by recombinations with markers D9S1680 and D9S1786. These two families share an identical disease haplotype over 18 markers, inclusive of D9S278-D9S280. This provides strong evidence that the English families have the same ancestral mutation, which reduces the disease interval to <12.7 cM between markers D9S257 and D9S1851 in chromosome band 9q22. In the Portuguese family, we excluded linkage to this region, a result indicating that BDB is genetically heterogeneous. Reflecting this, there were atypical clinical features in this family, with shortening of the thumbs and absence or hypoplasia of the nails of the thumb and hallux. These results enable a refined classification of BDB and identify a novel locus for digit morphogenesis in 9q22.

Publication metadata

Author(s): Loughlin J; Oldridge M; Temple IK; Santos HG; Gibbons RJ; Mustafa Z; Wilkie AO; Chapman KE

Publication type: Article

Publication status: Published

Journal: American Journal of Human Genetics

Year: 1999

Volume: 64

Issue: 2

Pages: 578-585

Print publication date: 01/02/1999

ISSN (print): 0002-9297

ISSN (electronic): 1537-6605

Publisher: The American Society of Human Genetics


DOI: 10.1086/302255

Notes: Journal Article Research Support, Non-U.S. Gov't United states


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