Leukocyte alkaline phosphatase levels in multiple myeloma.

Leukocyte alkaline phosphatase levels (LAPL's) were determined in 62 patients with multiple myeloma over a 13-year period. Sixty of the 62 myeloma patients had consistently elevated LAPL's, one patient had normal LAPL, and one patient had an initially normal LAPL which later increased. Elevated LAPL's could not be correlated with age, hemoglobin levels, white blood counts, or elevation of the blood urea nitrogen. LAPL's did not change during objective or subjective responses to chemotherapy or with progression of disease. We suggest that some feature of myeloma may "turn on" an abnormal clone of cells which may be responsible for the elevated LAPL's in patients with multiple myeloma.