Unilateral leg swelling in a newborn

A female neonate was born with asymmetric lower limbs, the right leg appearing enlarged, with thickened, reddish-purple skin and ectasic superficial reticulum (figure 1A,B). Limb pulses were present and symmetrical. The girl's family history and prenatal scans were unremarkable. Laboratory findings were within the normal range, except for a mild thrombocytopenia (90 000/μL), which spontaneously resolved during the next few days. A leg X-ray and the Doppler analysis ruled out the presence of calcifications and venous varices, respectively. Ultrasound showed significant skin thickening, with marked dermal hypertrophy and hyperechogenicity. Magnetic resonance showed circumferential thickening of the derma, with mild hypertrophy of some perforating vessels (figure 2). A biopsy of the right thigh showed capillary malformations on histology.