Interstitial deletion of the short arm of chromosome 20 in arteriohepatic dysplasia (Alagille syndrome).

An autosomal dominant transmission of arteriohepatic dysplasia, or Alagille syndrome, with reduced penetrance and variable expressivity has been suggested from familial pedigrees, but the nature of the genetic defect and its chromosomal localization are not firmly established. We report the case of an 8-year-old boy with arteriohepatic dysplasia, in whom high-resolution chromosome study showed a partial deletion of the short arm of chromosome 20, which encompasses subbands p11.23 to p12.3. In situ hybridization and Southern blotting localized four restriction fragment length polymorphism probes within the deletion and another one distal to the deletion. Because one patient has already been reported to have arteriohepatic dysplasia and deletion of the short arm of chromosome 20, and six additional patients with such a deletion had major features of Alagille syndrome, this syndrome should now be assigned to chromosome 20p.