Heterozygous manifestations are not recognized. Classically, the diagnostic triad for Meckel Syndrome consists of polydactyly, encephalocele, and cystic dysplasia of the kidneys. Clinically, many cases of Meckel Syndrome present unexpectedly at birth following an uneventful pregnancy. Some patients present with oligohydrannios. Patients affected with Meckel Syndrome rarely survive beyond a few days to weeks, however, some have survived for up to two years of age.
Death usually occurs secondary to renal failure versus central nervous system defects.
As previously mentioned, the main manifestations of Meckel Syndrome include occipital encephalocele, polycystic kidneys, fibrotic changes of the liver. Additional frequently noted anomalies include polydactyly, cleft lip and or palate, microcephaly, microphthalmia, and small and ambiguous genitalia. Other CNS manifestations reported include anencephaly, hydrocephalus, aquaductal stenosis, Arnold Chiari malformation, Dandy Walker malformation, arachnoid cysts, cerebellar hypoplasia and polymicrogyria, any of which may occur with or without encephalocele. More specific examination of the kidneys in these cases usually reveals bilaterally enlarged diffusely cystic kidneys causing marked abdominal distention. Radiographically, these kidneys may resemble autosomal recessive polycystic kidneys, however, cysts in the latter are radially oriented.