Prenatal diagnosis of a neural tube defect: Meckel syndrome.

A severe neural tube defect diagnosed in a 191/2-week-old "at risk" fetus on the evidence of a markedly elevated alpha-fetoprotein level in the amniotic fluid, turned out to be an occipital myelocoele. However, the fetus also had polycystic kidneys and postaxial hexadactyly on all extremities. The karyotype was normal. These are the features of the rare Meckel syndrome, caused by a pleiotropic, autosomal, recessive gene, and one and possibly two other sibs were also affected.