Light Chain Proteinuria and Lysozymuria in a Patient with Acute Monocytic Leukemia

We present an unusual case of a patient presenting with both monocytic leukemia and plasma cell dyscrasia. Of interest, very high concentrations of monoclonal free light chain, Bence Jones protein (BJP),1 and lysozyme were found in the urine, and identification of lysozyme by immunofixation electrophoresis (IFE) required modification of the usual methods. An 83-year-old man entered the Veteran Administration Hospital from a nursing home with a complaint of failure to urinate. The patient was being followed for myelodysplastic syndrome. The patient was admitted to the hospital on the basis of dysuria and a low hemoglobin (reference intervals in parentheses) of 53 g/L (135–180 g/L). The white blood cell count was 8.1 × 109/L (5–10 × 109/L), with 61% monocytes. Pertinent blood chemistry results on admission were as follows: urea nitrogen, 0.9 g/L (0.07–0.22 g/L); creatinine, 0.06 g/L (0.006–0.014 g/L); potassium, 3.4 mmol/L (3.5–5.3 mmol/L); calcium, 0.076 g/L (0.092–0.107 g/L); total protein, 76 g/L (62–82 g/L); albumin, 24 g/L (35–50 g/L); IgG, 30 g/L (7.2–16.8 g/L); IgA, 2.6 g/L (0.69–3.8 g/L); IgM, 0.62 g/L (0.63–2.7 g/L); and κ/λ ratio, 0.49 (1.2–2.6). A monoclonal protein had not been detected previously, but results of the serum protein electrophoresis and immunonephelometric analysis performed on admission indicated a monoclonal IgG-λ concentration of ∼30 g/L. This profile is most consistent with myeloma. Bone marrow aspirates showed 30–40% monocytes/myeloblasts and 5–10% plasma cells. Radiologic examination, including bone radiography and computerized tomography, …