A Patient with Artifactually Low Serum High Density Lipoprotein Cholesterol Due to Waldenstrom Macroglobulinemia.

When very low or undetectable high density lipoprotein (HDL)-cholesterol (HDL-C) is encountered in clinical practice, a paraproteinemia should be suspected in the absence of genetic or more obvious secondary causes. We reported a case of artifactually low HDL-C in a 68-year-old man with a past medical history of vitamin B12 deficiency. Lipid panel showed total cholesterol (TC) 144 mg/dl, triglycerides (TG) 79 mg/dl, HDL-C 5 mg/dl, and low density lipoprotein (LDL) 123 mg/dl. HDL-C, which was determined three years prior to this presentation was found normal. The patient was prescribed extended release nicotinic acid. Further workup performed showed the ratio of APO B/APO A1 0.36 and direct LDL 28 mg/dl. In the absence of genetic or more obvious secondary causes, we hypothesized that low HDL-C in this patient was due to paraprotein interference in vitro with the liquid homogenous HDL assay. Serum protein electrophoresis demonstrated normal IgG and IgA and an abnormally high IgM at 3510 mg/dl (57-266). A bone marrow biopsy revealed Waldenstrom macroglobulinemia. A diagnostic workup for an isolated low HDL-C unmasking the diagnosis of Waldenstrom macroglobulinemia has been rarely reported. Care must be taken when using the homogeneous method for direct measurement of HDL-C as artifactually undetectable HDL-C might result in the mismanagement of patients with paraproteinemia.