A Tale of Two Rashes

Abstract

PRESENTATION A rash is often an important clue as to the etiology of a systemic illness. In this case, 1 patient developed 2 distinct rashes that led to two diagnoses both associated with C4 complement deficiency. A 72-year-old woman with endstage renal disease presented to our emergency department with an 8-day history of pain and swelling in her left arm. She recalled that she had experienced similar symptoms 4 months previously; at that time, she had been treated with angioplasty of an occluded vascular graft in the same extremity. Her medical history was otherwise significant for a hospital admission 10 years previously for management of malignant hypertension, dyspnea, and seizures. At that time, she had marked hypertension, peripheral edema, and bilateral pleural effusions. Her serum creatinine level was 2.4 mg/dL, and she had proteinuria (4.16 g protein per 24 hours). Antinuclear antibody testing was positive, with an atypical speckled pattern. Anti-Ro and anti-La antibodies also were positive (titer not reported), but her anti-double stranded DNA antibody titer was negative. Her rheumatoid factor level was mildly elevated (17 IU/mL; normal range, 0–15 IU/mL). Monoclonal IgM kappa and polyclonal IgG cryoglobulins were present at 3% total concentration. Complement testing yielded a normal C3 level (102 mg/dL) but no detectable C4. Hepatitis B surface and core antibodies, but not surface antigen, were detected. Hepatitis C testing