Discordance for the Kleeblattschädel anomaly in monozygotic twins with thanatophoric dysplasia.

We describe monozygotic twins with thanatophoric dysplasia who were discordant for the Kleeblattschädel anomaly, but were identical in all other respects, including the histologic appearance of the endochondral growth plate. The observation suggests that the skull anomaly represents a variable manifestation of thanatophoric dysplasia, and that its occurrence in an infant with this bone dysplasia should not alter the low recurrence risk generally given.