Patients presenting skin disorders with a probably vascular origin are often addressed to the vascular medicine unit. In general, the diagnosis of telangiectasia is straightforward but in certain rare clinical forms may be misleading. We report the case of a female patient presenting unilateral circumscribed telangiectasia on the left arm. History taking revealed that these lesions were congenital and had become accentuated during a recent pregnancy. The unilateral localization was highly suggestive, following Blaschko's lines. We retained the diagnosis of congenital unilateral nevoid telangiectasia syndrome exaggerated by pregnancy and the consequent hyperestrogenism. While it may be rather easy to rule out medical emergencies such as purpura, identifying the etiology of telangiectasia may be quite difficult, implying a careful, precise and complete history taking. Unilateral nevoid telangiectasia is a rare entity to be recognized. The underlying pathogenic mechanism remains to be elucidated.