C3 deficiency presenting as Raynaud's phenomenon in a 6‐year‐old girl with a persistent erythematous rash

Summary A 6‐year‐old girl presented with a history of a persistent groin and axillary fold erythematous scaly rash, present since birth and unresponsive to topical steroids. Raynaud's phenomenon affecting hands and feet was noted and a level of C3, 50%, of normal, was detected with a positive anti‐nuclear antibody, IgG class speckled pattern at a titre of 1 in 40.