LAUSR

A previously healthy 15-year-old boy presented to our hospital with pain and purpura of his left thigh after an intramuscular injection in that leg. Ten days prior, he had presented to a referring hospital’s emergency department for nausea and vomiting and was given 20 mg of intramuscular dicyclomine. He reported severe pain at the time and site of injection. Within a few hours, he noticed swelling and purpura overlying the site of injection. Over the next 2 weeks, the swelling persisted and the purpura intensified, becoming black centrally (Figure A and B). Pain worsened over this period, initially restricting use of the leg, then preventing any weight bearing, prompting his admission to our hospital 10 days after the injection. He also reported numbness and occasional tingling of the skin involved. The patient denied fever or chills, and his nausea and vomiting had resolved. Findings of a physical examination were significant for retiform purpura of the left thigh, approximately 8 × 12 cm in size. Palpation of the area elicited severe pain. Popliteal, posterior tibial, dorsalis pedis, and femoral pulses were strong. There was no swelling of the remainder of the leg, and findings of joint examinations were normal. Sensation was intact throughout the leg with the exception of the skin involved, which had diminished light touch. Blood test results revealed a normal complete blood cell count, normal coagulation profile, and an elevated creatine phosphokinase level of 477 U/L (normal range, 22-198 U/L; to convert to microkatals per liter, multiply by 0.0167). Magnetic resonance imaging of the thigh was completed, and a skin biopsy was performed for culture and histology. Retiform pupura 2 d after injection A Worsening retiform pupura 13 d after injection B