The most common cause of hyperviscosity syndrome is Waldenstrom macroglobulinemia. Other causes may include: Acute myeloid leukemia (AML). Chronic hypoxia, lack of oxygen to your tissues. Connective tissue diseases, such as rheumatoid arthritis or lupus. Cryoglobulinemia. Essential thrombocythemia, too many blood platelets. Leukemia. Multiple myeloma. Paraneoplastic syndromes. Polycythemia vera. Sjögren’s syndrome. Myelodysplastic syndrome.