Background: Waldenström’s macroglobulinemia is a rare malignant monoclonal gammopathycharacterized by the production of excess IgM monoclonal protein. It presents with symptoms related to the infiltration of the hematopoietic tissues or the effects ofmonoclonal IgM in the blood. We present a case report to have much more experience of diagnosis of rareentity of maglinant lymphoid proliferation.Case report: A 70-year-old male hospitalized with weakness, bruising, splenomegaly, no hepatomegaly,no lymphadenopathy. Red blood count: 1.1 x1012/l, Hb 45g/l, white blood count: 9.9 x109/l (74% lymphocytes,11% plasmacytoid lymphocytes, 1% plasmocyte, 11% neutrophils (1.08 x109/l), 3% monocytes), and plateletcount: 15 x109/l. LDH, liver and renal function tests were normal. Serology for HIV, hepatitis B and hepatitisC were normal. Karyotype had no metaphase cells. MYD88 L265P mutation was negative. The bonemarrow aspiration and biopsy showed a massive proliferation of small lymphocytes (61% lymphocytesmixed with plasmacytoid lymphocytes (17%) and plasma cells (3%). Immunophenotype: Positive for CD19,CD22, CD79a. Negative for CD20, CD34, CD10, CD5. Elevated erythrocyte sedimentation rate: 49mm/1st.Rouleaux formation. Protein 90g/l
Albumin 27.5g/l
A/G: 0.44
Monoclonal Gamma: 51.1g/l
IgM: 5.47g/dl.The bone SPECT image showed an abnormal concentration of radiation at the front arc of the rib 5 andthe left side of the ribs 6 and 7. High-risk prognosis with 4 prognosis points according to the InternationalPrognostic Scoring System.Conclusion: Diagnosis: A Waldenstrom’s Macroglobulinemia Case with Bone Lesions and CD20negative.