Central nervous system lesions in hypomelanosis of Ito: an MRI and pathological study.

A severe form of hypomelanosis of Ito is reported, which presented as fetal macrocephaly and neonatal epileptic encephalopathy. Lymphocyte karyotypes were normal. MRI showed an absence of delineation between cortical grey matter and white matter. The prominent neuropathological finding was an abnormal cortical morphogenesis, with the co-existence of cells migrating normally and cells exhibiting arrêt en route or even the complete absence of migration. Intense astrocytic reaction with moderate dystrophic features was present. Juxtaposition of two migration behaviours in the neural cells paralleled the cutaneous findings and reinforced the hypothesis of a genetic chimerism.