Meckel-Gruber syndrome concomitant with Dandy-Walker malformation: prenatal sonographic diagnosis in two cases.

Meckel-Gruber syndrome is an autosomal recessive disorder which comprises a characteristic triad of major abnormalities: renal cystic dysplasia, occipital encephalocele, and postaxial polydactyly. Because of the recessive inheritance, prenatal sonographic diagnosis is paramount for informed genetic counselling of affected pregnancies. However, Meckel-Gruber syndrome may demonstrate variation in phenotypic expression when some malformations are different from those traditionally accepted and cases may be evaluated as a different syndrome. The aim of this paper is to emphasise the phenotypic variability in Meckel-Gruber syndrome, and the importance of the prenatal sonography in the diagnosis. We also suggest that Dandy-Walker malformation or Dandy-Walker variant be accepted as one of the malformations which occur in the central nervous system as a part of the syndrome.