A 32-year-old man was admitted to the hospital because of IgG antibody and Coombs'-positive hemolytic anemia resistant to corticosteroid treatment.The patient had been well until about five months earlier, when he began to have low-grade fever, night sweats, and nonpleuritic pain in the right deltoid region. Laboratory tests were performed at another hospital. The urea nitrogen, creatinine, glucose, total protein, ferritin, and lactate dehydrogenase levels were normal; the results of other tests are shown in Tables 1, 2, and 3. A radiograph of the chest was normal. Microscopical examination of an aspirated bone marrow specimen showed erythroid hyperplasia. A tuberculin skin test was negative, with positive controls. Prednisone (80 mg daily) was administered. The fever and sweats subsided, and the hematocrit rose to 25.5 percent.Two months before admission, the patient was seen at this hospital. Treatment with prednisone was continued. Several weeks before admission the hematocrit decreased to 18 percent. Five days before admission, a computed tomographic (CT) scan of the thorax (Fig. 1) showed bulky right axillary lymphadenopathy. A CT scan of the abdomen and pelvis (Fig. 2) revealed hepatosplenomegaly and lymphadenopathy, principally in the para-aortic, aortocaval, and right pelvic regions. A magnetic resonance imaging (MRI) examination of the right arm (Fig. 3) showed an abnormal signal in the medulla of the humerus, a finding consistent with regenerating marrow. Microscopical examination of an aspirated bone marrow specimen showed marked trilineage hematopoiesis. Microscopical examination of thick and thin blood smears showed no *To convert value to micromoles per liter, multiply by 0.1791.