Adult hypophosphatasia.

A case of adult hypophosphatasia under treatment with a high orthophosphate (P1) intake is described. The patient is a 53-year-old woman. Her symptoms have progressed for seven years, and it has been necessary to perform osteosynthesis of both crura. The diagnosis rests upon a characteristic clinical picture, low serum alkaline phosphatase activity, high urinary excretion of phosphoethanolamine, and an invariably elevated concentration of inorganic pyrophosphate (PP1) in plasma accompanied by a very high excretion of this compound in the urine. An improved technique allowed specific determinations of microquantities of PP1 in biologic materials. The concentrations of PP1 in the plasma and urine remained unchanged when the patient's intake of phosphorus was increased to 1.98 g/day. The PP1/P1 ratio in the urine was 10-20 before treatment. During treatment P1 excretion increased. PP1 excretion did not change, and the ratio decreased to around 7. The renal tubular transport of PP1 probably was saturated, and therefore PP1, which was circulating in abnormally high concentrations in the patient's fluids, could not be removed by loading with P1. Four months of treatment did not benefit the patient.