Frequency of Ectopic Calcifications Among Patients With Hypophosphatasia in the Global HPP Registry

Ectopic calcifications have been observed in patients with hypophosphatasia (HPP)—a rare, inherited, metabolic disorder characterized by reduced enzymatic activity of tissue nonspecific alkaline phosphatase. The natural history of these calcifications is poorly understood. Using data from the Global HPP Registry, a cross-sectional, observational analysis was conducted to better understand the prevalence of nephrocalcinosis and eye calcifications in patients with HPP in the absence of treatment with the enzyme replacement therapy, asfotase alfa. The association between hypercalcemia (serum calcium ≤10.3 mg/dL [normal]; 10.4–11.9 mg/dL [mild hypercalcemia]; ≥12.0 mg/dL [moderate to severe hypercalcemia]) and ectopic calcification was also evaluated. Of the patients in the study population with renal ultrasound data (n=327), 11.0% had nephrocalcinosis; no patients had severe nephrocalcinosis. In children (aged