In addition, ~30% of diagnosed cases of CM–AVM have AVMs in the skin, muscle, bones of the face, ears, thorax, extremities, brain and spine.4 In HHT, AVMs can also be present in the brain but differ from CM–AVM in that the liver and lungs can be affected as well.4 Although patients with RASA1 mutations may be distinguishable upon careful examination, there is significant phenotypic overlap with HHT possibly confounding diagnosis. This evidence concerns the gene RASA1 and cutaneous mastocytosis.