Glomuvenous malformations (GVM) are hamartomas characterized histologically by glomus cells, which should be distinguished from glomus tumors. Familial GVM are rare, often present as multiple lesions, and exhibit familial aggregation, with autosomal dominant transmission. GVM are caused by mutations of the glomulin (GLMN) gene on chromosome 1p21-p22. Their development is thought to follow the ‘two-hit’ hypothesis, with a somatic mutation required in addition to the inherited germline mutation. We describe a novel GLMN mutation in an Italian family with GVM in which some members present with the less commonly observed phenotype of solitary lesions. A second somatic ‘hit’ mutation in GLMN was not discovered in our family. We further provide histological, immunohistochemical and electron microscopic data exhibiting the classic features of GVM. The diagnosis of GVM is critical because of distinction from venous malformations and blue rubber bleb nevus syndrome, which may demonstrate clinical similarities but require different treatment.