Bier spots and unilateral nevoid telangiectasia: more than just a coincidence*

Dear editors: Twin spotting (didymosis) means the coexistence of discrete areas of skin in close spatial and temporal proximity, differing clinically and genetically from each other, and from the background skin. This is a type of mosaicism caused by somatic recombination. A growing list of previously unexplained skin conditions has been attributed to this phenomenon.1 We describe the case of a 12-year-old Caucasian female with numerous macular, ovoid, hypochromic lesions of about 5mm on the dorsum of the left hand and arm. Some of the lesions were confluent, surrounded by erythematous, blanching skin. (Figures 1-3). These lesions were asymptomatic, began at birth and were induced by pendent position of the arm, disappearing a few seconds after its elevation.