Glomuvenous malformations
Glomuvenous malformations (GVM; MIM 138000) are a type of vascular malformation mainly involving the skin and subcutis of the extremities. GVM are often present at birth and slowly expand. Typically they are nodular, multifocal hyperkeratotic lesions with a cobble stone appearance. They are often painful on palpation, pink to dark blue in color and cannot be emptied on compression. These features distinguish GVM from typical venous malformation. Histologically, GVM are characterized by distended vascular channels surrounded by mural glomus cells. Glomus cells are considered to be abnormally differentiated vascular smooth muscle cells. GVM are caused by loss of function mutations in the glomulin gene. Although inheritance is considered to be autosomal dominant there is some evidence that suggests a "second hit" somatic mutation (paradominant inheritance) is required for the lesions to develop.
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