Discordant expression of tuberous sclerosis in monozygotic twins

A set of 20-year-old female Japanese twins, most probably monozygotic, had clinical evidence of tuberous sclerosis (TS). They were discordant for symptoms. One of the twins exhibited facial red-brown papules (adenoma sebaceum), a dorsal shagreen patch, intracerebral calcifications, angiomyolipoma in the right kidney, and hypopigmented macules; the other had only a few hypopigmented macules. Modification of TS gene expression by the effects of environmental (extrinsic) factors is suggested.