TP53 mutations were much more common in whole-skin FAF biopsies (dermis + epidermis; n = 18, range 1–36 mutations, median 5 mutations) than in FAF biopsies that were dermis only (n = 5, range 0–2 mutations, median 1 mutation) (P = 0.004, Mann-Whitney test; Figure 3B), suggesting that TP53 mutations were occurring mainly in keratinocytes in these samples, rather than fibroblasts in TSC facial skin, consistent with previous studies in individuals without TSC (15, 18). The gene discussed is TP53; the disease is tuberous sclerosis.