Dominantly inherited unilateral terminal transverse defects of the hand (adactylia) in twin sisters and one daughter.

Most previous cases of unilateral terminal transverse defects of the hand have not been familial. Several previously reported cases of apparent autosomal dominant inheritance of such defects have subsequently been reclassified as type B brachydactyly. We report a pair of adult twin women with unilateral terminal transverse defects affecting the left hand in one woman and the right hand in the other woman. The latter woman has one daughter with a unilateral terminal transverse defect affecting the left hand. The hand anomaly is characterized by absence of the terminal portions of digits 2 to 5 with a mildly hypoplastic thumb (adactylia). Tiny nail remnants are evident on the remaining digital stumps, and no soft tissue syndactyly is apparent. At 2 years of age, the daughter has hypoplastic first, fourth, and fifth metacarpals with no ossification of the second or third metacarpals or any of the phalanges. The affected mother has hypoplastic metacarpals for digits 2 to 4 and a vestigial fifth proximal phalanx on the affected hand, with no other phalanges evident by roentgenogram other than those of the thumb. The mother's twin sister has similar findings, except the ossified phalangeal remnant is on her second and third fingers rather than her fifth finger. Doppler flow arterial patterns appeared normal in each hand of affected family members. The other hand and both feet are clinically and radiologically normal in each case, and the family history is negative for any other individuals with limb anomalies. A review of the literature suggests that this family may very well be unique.

Variation in argininosuccinate synthetase activity in amniotic fluid cell cultures: implications for prenatal diagnosis of citrullinemia.

Argininosuccinate synthetase activity was measured in amniotic fluid cells cultured from 25 normal fetuses and from 2 fetuses at risk for citrullinemia. Among the 25 control lines, argininosuccinate synthetase was low in epithelial-like cultures and high in more fibroblast-like cultures. The radioactivity incorporated from 14C-citrulline into protein was proportional to argininosuccinate synthetase activity. The activity of argininosuccinate lyase, the next enzyme in the urea cycle, was unaffected by a predominance of one or the other cell type. Argininosuccinate synthetase was low but detectable in cells from the two fetuses at risk for citrullinemia. The pregnancies were continued and both resulted in clinically normal females. Thus factors such as predominant cell type may affect area cycle enzyme activity in cultured amniotic fluid cells and should be taken into consideration in attempts to diagnose citrullinemia prenatally.