A case is described of a boy five years old who suffered from left-sided muscular weakness since the first months of life and from absences since the second year of life. He died of valproate-induced hepatic insufficiency. Autopsy of the brain revealed meningio-angiomatosis, a rare but rather benign disorder usually characterized by narrow meningothelial proliferations abutting upon cortical plaques and exhibiting proliferations of small vessels with perivascular cuffs of fibroblast-like cells. The peculiarities were that the case lacked any leptomeningeal calcification - in line with the patient's age being the lowest so far reported for pathologically verified meningio-angiomatosis - and also exhibited intracortical clusters of mesenchymal cells that did not form vessels ("free fibroblasts"). Immunohistochemically perivascular cells were negative for S100, GFAP, desmin and factor-8-related antigen and were embedded in interstitial collagen of types III and VI as well as procollagen I, while "free fibroblasts" were surrounded by deposits of basement membrane collagen type IV. The results are consistent with a meningothelial origin of perivascular cells and "free fibroblasts".