TEK and cutaneous mastocytosis: Inherited loss-of-function genetic mutations have been found in bone morphogenic protein (BMP) and transforming growth factor-β (TGF-β) receptor genes in hereditary hemorrhagic telangiectasia (HHT) [242–246]; several CCM genes causing cerebral cavernous malformations [247–249], glomulin in inherited glomuvenous malformations (GVM) [250], RASA1 in capillary malformation–arteriovenous malformations (CM–AVM) [251], and weak germline gain-of-function (GOF) mutations in the TIE2/TEK gene appear to be the main genetic cause of capillary–venous malformations [252, 253].