“…If the mutations occur early on in development and affect several tissues, one sees syndromic disorders with a particular, characteristic nevus (3). Worthy of note here is Schimmelpenning syndrome, which has been known clinically for decades and which can affect in particular the CNS, eyes, and bones (osteomalacia, hypophosphatemic rickets) (26), with mosaic mutations detected in HRAS, KRAS, and NRAS (10). S Its identification as a mosaic disorder was able to explain the remarkable variability in clinical symptoms.…”