Somatic mosaic pathogenic variants cause the majority of CMs, but germline pathogenic variants in RASA1 and EPHB4 cause the familial capillary malformation (CM) syndromes, capillary malformation-arteriovenous malformation 1 and 2 (CM-AVM1 and CM-AVM2), respectively [4, 5]. The gene discussed is RASA1; the disease is congenital myasthenic syndrome.