Abstract
A 54-year-old woman with multiple sclerosis treated with interferon-β (IFN-β)-1b for 15 years presented with sustained hypertension (240/124 mmHg) and retinal bleeding. She had proteinuria, anemia, thrombocytopenia, elevated serum creatinine levels, and haptoglobin depletion. Intravenous nicardipine stabilized her blood pressure, but her renal function and platelet count deteriorated. The initial disintegrin-like metalloprotease with thrombospondin type 1 motifs 13 (ADAMTS13) activity was 28% of normal without its inhibitor. The subsequent peripheral appearance of schistocytes suggested thrombotic microangiopathy (TMA). After IFN-β-1b cessation, the platelet count increased, and the blood pressure stabilized. The ADAMTS13 activity normalized, although the creatinine level did not. TMA may develop after the long-term use of IFN-β without adverse events.