PTCH1 and Gerstmann syndrome: The majority of GS cases are driven by mutations in the tumor suppressor gene (TSG) Patched (Ptch) and/or the G-protein coupled receptor smoothened (SMO)6, leading to activation of Gli transcription factors (Gli1, 2, 3), and thereby uncontrolled proliferation of basal cells and ultimately BCCs growth in the skin of affected individuals7–10.