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- AKT1: This is a human gene. Genetic variants in AKT1 are found in proteus syndrome.
- Angiosarcoma: A specific type of malignant vascular tumor
- Arteriovenous Malformation (AVM): A fast-flow vascular malformation in which multiple direct connections between the arterial and venous system result in low resistance flow, with consequent enlargement of adjacent arteries and veins (sometimes referred to as ‘feeding vessels’). Approximately one- third of AVMs are evident at birth, but they can present at any age. AVMs tend to gradually enlarge over time, but this is highly variable. Some remain stable in size for long periods. Some AVMs enlarge at puberty and during pregnancy. The genomic causes of AVMs are heterogeneous. Some are due to germline genetic variants, as seen in hereditary hemorrhagic telangiectasia (HHT), capillary malformation AVM (CM- AVM)1 or capillary malformation AVM (CM-AVM) syndrome 2 (CM- AVM1, CM-AVM2) or Cowden syndrome due to germline PTEN genetic variants. However, most AVMs are sporadic and are caused by somatic genetic variants which tend to occur in the RAS/MEK/ERK pathway, the best documented genetic variants being gain of function genetic variants in genes MAP2K1 and HRAS, and less often in BRAF. A minority of AVMs occur as part of a syndrome: capillary malformation AVM (CM-AVM) syndrome; hereditary hemorrhagic telangiectasia (HHT); and PTEN hamartoma syndrome. AVMs are also sometimes seen in neurofibromatosis type 1.AVMs which occur in the brain have traditionally been managed by separate specialists from those occurring elsewhere in the body and therefore tended to be regarded as distinct lesions. With growing evidence that these lesions are caused by the same genetic variants as those elsewhere in the body, it has become clear that differences are likely due to anatomic location rather than intrinsic differences. AVMs in the brain most often remain unrecognized until an episode of bleeding. “AVMs” in the lung and liver are particularly associated with HHT and generally correspond to arteriovenous fistulas.
