RASA1 and angioosteohypertrophic syndrome: RASA1-related disorders follow an autosomal dominant pattern of disease inheritance and mutations in RASA1 result in a number of syndromes such as CM–AVM syndrome, Parkes Weber syndrome and 5q14.3 neurocutaneous syndrome.4 The RASA1 gene encodes p120RasGAP, which functions as an activator of non-oncogenic RAS-p21 GTPase activity.