70 year old male, presented with easy fatigue, weakness and developing pancytopenia since last 2 months with no organomegaly.

Hemogram was ordered which showed Hb of 8.0 g/dl, TC of 3920/cumm and 56000/cumm platelets. Peripheral smear showed macrocytic anemia with marked rbc rouleaux formation and atypical lymphocytosis with many plasmacytoid lymphocytes.

Based on this findings, protein electrophoresis and free light chain assay was ordered which showed M band with high free lambda light chain. Subsequent BM examination showed solidly cellular marrow with predominantly small atypical lymphocytes with intermixed plasmacytoid lymphocytes and plasma cells. Flow cytometry of marrow aspirate showed low grade B-cell lymphoproliferative neoplasm.

Based on these findings, diagnosis of LPL was established which was confirmed by MYD88 L265P mutation.

LPL is an indolent disease with median survival of 5-10 years. It affects adults with median age in seventh decade of life with male predominance. Bone marrow involvement is common wit very few cases involve lymph nodes. Cases without MYD88 L265P mutation have adverse prognosis and low response to ibrutinib.

Waldenstrom macroglobulinaemia is defined as LPL with marrow involvement and IgM monoclonal gammopathy of any concentration.

Morphological identification of mixture of small lymphocytes with plasmacytoid lymphocytes and RBC rouleaux foramtion are the key features to initial diagnosis.