Loss of TSC1 or TSC2 results in benign tumor formation in various organs (4), including subependymal nodules (SEN), subependymal giant cell astrocytomas (SEGA) and cortical tubers of the brain, smooth muscle tissue and cystic changes in the lungs (lymphangioleiomyomatosis, LAM), skin fibromas and angiofibromas, and cardiac rhabdomyomas in infants (5, 6). The gene discussed is TSC1; the disease is subependymal giant cell astrocytoma.