A family with popliteal pterygium syndrome is reported: two children presented a mild form of the syndrome, while their mother exhibited full expression of the gene. Only 11 families with 29 affected members and 25 sporadic cases have been published. This malformation syndrome is inherited in an autosomal dominant pattern, but environmental factors or genetic heterogeneity cannot be excluded in sporadic occurrences. The variability of expression is discussed and a comparison with previously published familial cases is made: minor anomalies, if present in relatives of patients with full gene expressions, are as helpful in making the diagnosis as are major abnormalities. Careful evaluation of the proband's family is essential for diagnosis and subsequent genetic counselling
