The mild form of pseudoachondroplasia. Identity of the morphological and biochemical alterations of growth cartilage with those of typical pseudoachondroplasia.

A 9-year-old boy from an incestuous union presented with mild clinical and roentgenological manifestations of pseudoachondroplasia. Tibial growth cartilage was obtained during a routine orthopedic procedure. Microscopic, histochemical and biochemical analysis showed changes identical to those of 6 sporadic cases of typical pseudoachondroplasia. The results support a concept of pathogenetic homogeneity of pseudoachondroplasia.