An 18-year-old man complained of intermittent low back pain and fatigue. In 2008, an 18-year-old man complained of intermittent low back pain with frequent relapses, relieved by non-steroidal anti-inflammatory drugs (NSAIDs). In July 2009, he was admitted to a local hospital due to severe low back pain and fatigue. Initial laboratory evaluation revealed severe anemia (Hb concentration, 40 g/L), increased mean corpuscular volume (MCV; 122.7 fl); mild leucopenia (WBC 3.8 × 109/L); and normal platelet count. His blood folate and vitamin B12 concentrations were slightly decreased. However, he refused to undergo a bone marrow test. He was treated with red blood cell transfusion plus folic acid and vitamin B12; however, his symptoms were not relieved. Subsequently, in August 2009, he was referred to our hematology department for evaluation and further management of the severe anemia. He denied having traveled or being in contact with patients with tuberculosis or other infectious diseases recently. No sexual history was reported. His mother and father were healthy. There was no positive family history. The patient had no previous disease history. No personal and family disease history. Examination revealed pronounced skin pallor, a body temperature of 38.2 °C, and a pulse rate of 102 bpm. No dysmorphic features were observed. Hematological tests showed normocytic anemia (Hb 60.7 g/L), normal MCV, and leukocyte and platelet counts. Vitamin B12 and folate levels were increased. The blood reticulocyte count was 2.4%, serum ferritin concentration was 405.2 ng/mL, ESR was 160 mm/h, and C-reactive protein (CRP) concentration was 145.42 mg/L. The Rous test and the direct and indirect antiglobulin Coombs tests were negative. The CD55 and CD95 expression on red blood cells and granulocytes, and lactic dehydrogenase and bilirubin values were normal. The blood coagulation panel and the urine test results were normal. Blood creatinine, alanine aminotransferase, and aspartate aminotransferase levels were normal. Furthermore, titers for antinuclear antibody, anti-extractable nuclear antigen antibody, antineutrophil cytoplasmic antibody, rheumatoid factor, immunoglobulin, and complement factors (C3/C4) were normal. Tests for human immunodeficiency virus, syphilis, hepatitis B, hepatitis C, and Parvovirus B19 were negative. Blood bacteria culture and the tuberculin purified protein derivative test were also negative. Tumor markers such as AFP, CEA, CA125, CA199, and PSA were all negative. Bone marrow aspiration revealed hypocellular marrow with single erythroid dysplasia; however, ringed sideroblasts were absent in the sample obtained in August 2009. The cytogenetic test was normal. Therefore, a diagnosis of MDS could not be established. The patient received a blood transfusion, NSAIDs, analgesics, and antibiotics (cefuroxime, sulperazone, meropenem, imipenem/cilastatin, and azithromycin). However, the patient still experienced a low-grade fever and pain. Abdominal ultrasonography showed splenomegaly (5.7 cm thickness). Computed tomography (CT) of the chest and the abdominal organs, and magnetic resonance imaging of the thoracic and lumbar vertebrae did not show any abnormalities. Tc-99m bone scintigraphy imaging showed active bone metabolism of the T9-11 and L4 vertebrae, the right sacroiliac joint, and both the knee joints.