X-linked congenital hydrocephalus.

In this report we describe a Dutch family with ten cases of X-linked recessive congenital hydrocephalus with a high perinatal mortality. In three cases necropsy has confirmed the diagnosis. In the best documented case the most striking features are absence of obstruction or stenosis of the aqueduct and congenital malformation of the cerebral cortex. On the basis of our findings and on reviewing the literature, the hypothesis is put forward that the defective gene on the X-chromosome is responsible for a pathological influence on cerebral cortex development and extraventricular CSF pathways. The expressivity of the genetic defect may be variable, causing extreme phenotypic variants (CHC and/or MR) under the influence of the different modifying genetic or environmental factors. Genetic counselling is difficult in families with no X-linked CHC precedent, since the mutant gene rather produces a communicating HC, secondarily complicated by narrowing of the aqueduct, and as at present there is no way of detecting beforehand heterozygote carriers.