A Rare Combination: Cold Agglutinin Disease Followed by Waldenström Macroglobulinemia—A Case of Early Treatment Response

Background and Clinical Significance: Waldenström macroglobulinemia (WM) is a rare, indolent B-cell non-Hodgkin lymphoma, characterised by the presence of monoclonal immunoglobulin M (IgM) and lymphoplasmacytic infiltration of the bone marrow. It is often associated with various haematological and systemic disorders, including previous cold agglutinin disease (CAD), a condition where cold-sensitive antibodies lead to haemolysis. Case Presentation: A 55-year-old male patient was admitted to the Internal Diseases Ward with symptoms of weakness, reduced effort tolerance, and weight loss, along with life-threatening normoblastic anaemia (haemoglobin Hb: 3.90 g/dL). Initial blood tests raised suspicion of CAD due to the presence of multiple blood clots, as well as a decrease in lymphocyte and neutrophil counts. CAD was then confirmed by a cold agglutinin titre of 1:2000 and direct antiglobulin test (DAT 4+). Two weeks later, upon transfer to the Haematological Diseases Ward, further investigation revealed elevated IgM levels (up to 31.55 g/L). Additional diagnostic tests, including serum protein electrophoresis, imaging, multiparametric flow cytometry, and bone marrow biopsy, confirmed the diagnosis of WM. The L265P MYD88 mutation test was positive. Treatment with intravenous rituximab was initiated, followed by bendamustine/rituximab (BR) therapy protocol as first-line treatment. After two cycles, the patient’s clinical condition and laboratory results significantly improved, with a marked reduction in IgM (<0.4 g/L). Hb levels steadily rose to 12.60 g/dL, eliminating the need for further blood transfusions. Conclusions: This case highlights the importance of recognising the coexistence of CAD and WM, which may present with overlapping clinical features, including life-threatening anaemia. Extensive diagnostics and prompt treatment with combination therapy can lead to effective clinical improvement.