Such may be the case in fibrous dysplasia/McCune-Albright syndrome (FD/MAS, which are caused by post-zygotic, somatic GNAS mutations) and Schimmelpenning-Feuerstein-Mims syndrome (which both feature bone lesions and café-au-lait spots), as well as in isolated linear nevus sebaceous syndrome (the latter two caused by post-zygotic somatic KRAS, HRAS or NRAS mutations). The gene discussed is GNAS; the disease is fibrous dysplasia.