We studied a boy with macrocephaly, hypotonia, pigmentary retinopathy, unilateral whorled hypopigmented skin lesions, and seizures. Skin biopsy confirmed the clinical diagnosis of hypomelanosis of Ito. Postmortem examination at age 22 months revealed a severe neuronal migrational defect that altered the cerebral cortex architecture of white matter. There were many gray matter heterotopias characterized by altered neurons and giant cells. Electronmicroscopy revealed the astrocytic nature of the giant cells. Embryologic migration of both melanoblasts from neural crest and cortical neurons occurs in the second trimester, suggesting a common mechanism for the developmental pathology of skin and brain.