Autosomal dominant tetramelic postaxial oligodactyly.

Postaxial limb deficiencies are most frequently unilateral and sporadic with deficiencies of the ulnar ray about one-third as common as those affecting the radial ray. Postaxial deficiency occurs in a number of genetic and sporadic syndromes, but isolated inherited tetramelic, postaxial oligodactyly has to our knowledge not been described. We report an affected mother and her 3 affected children from a 4-generation family with apparent autosomal dominant, non-syndromic, tetramelic, postaxial oligodactyly. The affected individuals manifest a very uniform pattern of postaxial deficiency ranging from complete absence of the 5th metacarpals, metatarsals, and phalanges to complete absence of the 5th metacarpals and metatarsals, but with some residual distal 5th phalanges. Limb buds may be considered a single developmental field with development proceeding rostral to caudal. Digit formation is apparently controlled by the zone of polarizing activity which releases a diffusible morphogen specifying positional information along the anterior/posterior axis. Recent investigations using chick and mouse embryo models suggest that 5' members of the Hox-4 gene cluster are responsible for interpreting this positional information to effect digit formation. The present family may represent a defect in Hox-4 gene patterning of hand and foot formation, an abnormality in morphogen gradient formation or alternately an inability of the most ulnar rays to respond to morphogen (receptor defect).