Phenotypic variation in Meckel syndrome.

Four sibs are described with Meckel syndrome, an autosomal recessive disorder with multiple abnormalities. Each sib manifested only two of the three cardinal sings of Meckel syndrome - encephalocoele and polycystic kidneys, lacking polydactyly. The literature is examined to assess the phenotypic variation of the condition: 57% of cases have all the three major abnormalities, 16% have the two found in this family, and the remainder exhibit other variations. In 9 of 17 families where more than one sib is affected, manifestation between sibs is the same, but in the only other two families with as many as four affected sibs, there is variation in expression between sibs.