Klippel–Trenaunay syndrome is easily diagnosed at birth but sometimes slips past doctors, according to Indian dermatologists who found the rare genetic condition in a three-year-old boy.

First reported in 1900, the disorder — also known as hemangiectatic hypertrophy syndrome or angio-osteohypertrophy syndrome — has unknown aetiology, with no clear racial or sex associations, said doctors from Datta Meghe Medical College in Nagpur.

The incidence of Klippel–Trenaunay syndrome (KTS) is around one in every 100,000 births.

In their case, the patient presented with raised skin lesions on his left leg and notable limb size discrepancy compared with his right leg.