Familial recurrence of terminal transverse defects of the arm.

Three families in which relatives were concordant for upper limb terminal transverse defects are described. These families and previously reported ones with similar recurrence of terminal transverse defects are reviewed and analyzed. It is suggested that, at least in part, the patterns of relatedness for these recurrences more likely are the result of a genetic contribution to the development of this birth defect, rather than such recurrences being solely due to chance.