Say syndrome: a new case with cystic renal dysplasia in discordant monozygotic twins.

Say syndrome is a rare condition characterized by cleft palate, short stature, and microcephaly. Abu-Libdeh et al. [1993: Am J Med Genet 45:358-360] described a case with cystic renal dysplasia. We describe monozygotic twins discordant for the syndrome with kidney dysplasia. A postzygotic mutation is proposed as the cause of this autosomal dominant syndrome in this case.