A 14-year-old girl was admitted to the hospital because of persistent throat pain, fever, fatigue, 25 pound weight loss, and leukopenia. On physical examination she was thin, ill-appearing, and had necrotic papules on the face and palpable cervical lymph nodes. Presumptive differential diagnosis included occult malignancy and infection. Numerous investigative procedures failed to elucidate a source. Vasculitis was eventually appreciated after repeat skin biopsy. Numerous serologic studies were performed and were notable for a very low level of the second component of complement without direct evidence of lupus erythematosus (LE) or other autoimmune conditions. A diagnosis of C2 deficiency-associated vasculitis was made. She was treated with high-dose prednisone and cyclophosphamide with resolution of her symptoms. Two years later she returned with marked malar erythema. Antinuclear and Smith antibodies were then detected and a diagnosis of LE was made. She was treated with hydroxychloroquine and sun-avoidance measures with clearance of the malar rash.