A 67 year old woman was admitted with a 20 days history of low back pain which did not improve despite the use of anti-inflammatory drugs. Five days before admission, drowsiness, fatigue, muscle weakness, polydipsia, polyuria and vomiting appeared, along with fever reaching up to 38 °C, but without chills. Clinical examination revealed pallor, fever (37.6 °C), mild painful hepatosplenomegaly and cervical microlymphadenopathy. The patient had a diminished level of consciousness, was confused and had difficulty concentrating, but had no focal neurological signs. The hematological tests were as follows: white blood cell count 12.6x10⁹/L (neutrophils 24%, lymphocytes 38%, monocytes 7%, metamyelocytes 3%, myelocytes 2%, plasma cells 26%), hemoglobin 8.4 g/dL, hematocrit 26.1% and platelets 68x10⁹/L. The plasma cells were very large, with a blast-like appearance and intense cytoplasmic basophilia (fig.1). However, a small population of typical plasma cells, with a clear perinuclear halo from Golgi apparatus, was also present. Serum biochemistry showed raised levels of LDH (990 IU/L), urea (124 mg/dL), creatinine (2.3 mg/dL), uric acid (8.6 mg/dL), calcium (13.6 mg/dL) and CRP (9.4 IU/L). Serum protein electrophoresis showed a small monoclonal band with quantitative abnormality. Immunofixation of gamma globulins revealed the presence of an IgGκ paraprotein. Radiographs of the axial skeleton revealed an osteolytic lesion in the third lumbar vertebra. The bone marrow aspiration showed 75% infiltration by plasma cells (fig. 2). Immunophenotyping of the peripheral blood showed that the plasma cells were positive for CD38 and for cytoplasmic immunoglobulin. Chemotherapy along with pamidronate was administered. However, no remission was achieved, and the patient died of sepsis two months later.