Ulnar ray defect in an infant with a 6q21;7q31.2 translocation: further evidence for the existence of a limb defect gene in 6q21.

Ectrodactyly is a developmental defect of the distal limbs characterized by marked clinical variability and genetic heterogeneity, also reflected in the observation of different chromosome abnormalities non randomly associated with longitudinal postaxial limb deficiencies. The one most frequently found in patients with split hand-split foot (SHSF) involves chromosome band 7q22. Recently, structural anomalies of chromosome 6q21 have been reported in 2 unrelated patients with SHSF, suggesting that this region may also contain genes responsible for limb development [Braverman et al., 1993. Am J Hum Genet, suppl 53: 410; Viljoen and Smart, 1993. Clin Dysmorph 2: 274-277]. We report on a third patient who had a de novo, apparently balanced t(6;7)(q21;q31.2) translocation and bilateral ulnar aplasia with postaxial oligodactyly. In spite of the different phenotypic effects observed in these 3 patients, we consider our case as further evidence that genes in 6q21 may play a role in distal limb development.