A case of acute monocytic leukemia with lysozyme-positive leukemic monocytes and normal serum lysozyme levels

We report a case of acute monocytic leukemia with normal serum lysozyme but with immunoperoxidase positivity for lysozyme in the leukemic blasts. The diagnosis of acute monocytic leukemia was made on the basis of cellular morphology, immunocytochemistry and cytochemistry. Discrepancy between serum lysozyme and intracytoplasmic lysozyme has not previously been reported in the literature. Levels of serum lysozyme may be misleading in cases of acute monocytic leukemia (FAB classification M5).