A 55-year-old Chinese man was referred to our department with a history of asymptomatic thrombocytosis over 1 year's duration. Apart from pleural tuberculosis 2 years ago treated with systemic anti-tuberculous therapy, his past medical history was unremarkable. His physical examination was unremarkable. A full blood count revealed a white blood cell count of 9.2x109/L with lymphocytes count of 3.0x109/L, haemoglobin 132g/L and platelet count of 629x109/L. Peripheral blood film showed thrombocytosis and there was no significant dysplasia. His biochemistry profile revealed a slightly raised total globulin level of 41.9g/L (normal range: 20-40g/L), uric acid: 507mumol/L (normal range: 208-428 mumol/L) and lactate dehydrogenase 242U/L (normal range: 109-245U/L). His serum immunoglobulin analysis revealed an elevated immunoglobulin M (IgM) of 21.5g/L (normal range: 0.46-3.04g/L), kappa light chain of 26.8g/L and lambda light chain lambda of 5.03g/L. Serum immunofixation confirmed the presence of monoclonal IgM. Ultrasound imaging study did not reveal lymphadenopathy, hepatomegaly or splenomegaly.
A bone marrow (BM) aspiration and trephine biopsy were performed. The BM aspirate morphology showed an excess of platelets and lymphoplasmacytoid lymphocytes (Figure 1A and B). The trephine reported cellularity of 55%, with increased numbers of lymphocytes and mature megakaryocytes with hyperlobated nuclei (Figure 1C). Flow cytometric immunophenotyping of his BM aspirate confirmed monoclonal B lymphocytes, which were positive for CD19, CD20 and cell membrane kappa light chain, but negative for CD5, CD10 and CD23 (Figure 2). Next-generation sequencing (NGS) with a 126-mutation panel was adopted to further investigate his gene/molecular mutation status which detected JAK2 V617F, MYD88 L265P, and ATM F1036L. BCR-ABL1 mRNA was not detected by quantitive real time-PCR.
Taken together, a diagnosis of ET with concomitant WM was made. He was treated with pegylated interferon and low-dose aspirin (100mg per day). After two months of treatment, his platelet count dropped to 324x109/L and IgM level to 11.80g/L.