rasopathy rasopathy the rasopathies are developmental syndromes caused by germline mutations (or in rare cases by somatic mosaicism) in genes that alter the ras subfamily and mitogen-activated protein kinases that control signal transduction, including: capillary malformation-av malformation syndrome autoimmune lymphoproliferative syndrome cardiofaciocutaneous syndrome hereditary gingival fibromatosis type 1 neurofibromatosis type 1 noonan syndrome costello syndrome, noonan-like legius syndrome, noonan-like noonan syndrome with multiple lentigines, formerly called leopard syndrome, noonan-like syngap1-related intellectual disability