A Lhermitte-Duclos type cerebellum hamartoma is reported in a woman wi
th a diffuse hamartomatous condition involving the breast, thyroid, co
lon, skin, and kidney. The family history demonstrated the autosomal d
ominant transmission of this hamartomatous syndrome, and indicated the
diagnosis of Cowden disease. This observation supports the recent hyp
othesis of Lhermitte-Duclos disease associated with Cowden disease as
being a single phakomatosis.