ALTERED CALCIUM-BINDING ABILITY OF PLASMA-PROTEINS AS THE CAUSE OF HYPOCALCEMIA IN LEPROMATOUS LEPROSY

This paper reports a study performed on 10 lepromatous leprosy outpati ents and on the same number of age- and sex-matched contacts. All of t he lepromatous patients were hypocalcemic, but plasma levels of ionize d calcium and the acid-base status were normal. The average daily food intake assessed through a questionnaire revealed adequate nutrition o f patients and controls. Plasma proteins and 1,25-dihydroxyvitamin D-3 and intestinal absorption of calcium were discarded as the causes of the hypocalcemia. In vitro experiments designed to investigate the eff ect of hydrogen ion concentration on the equilibrium between calcium i on and proteins revealed that, at normal pH values, plasma proteins fr om lepromatous leprosy patients bind a smaller fraction of total plasm a calcium than those from controls. This phenomenon produces a normal concentration of ionized calcium that determines a normal parathyroid status as indicated by the normal urinary excretion of hydroxyproline and plasma concentrations of alkaline phosphatase (total and bone isoe nzyme) and tartrate-resistant acid phosphatase.