ESPE Abstracts

Hypophosphatasia (HPP) is a genetic skeletal disease caused by loss-of-function mutations of ALPL encoding tissue-nonspecific alkaline phosphatase (TNSALP). The clinical presentation of HPP varies greatly, ranging from stillbirth without bone mineralization to findings in later life, such as delayed walking, short stature, skeletal deformities, bone pain, and pathologic fractures. The diagnosis is based on clinical examination, radiographic findings, biochemical parameters of reduced ALP activity, elevated serum and urine levels of TNAP substrates, and molecular analysis of the ALPL gene. The prognosis for the prenatal/infantile form is poor, with approximately 50% of patients dying within the first year of life from respiratory failure. Asfotase alfa, a bone-targeted, recombinant TNAP, has recently been developed to treat HPP complications. We describe the clinical features, biochemical findings, molecular analysis, and clinical experience of treatment with asfotase alfa over 6 years in patients with perinatal and infantile HPP in Korea. Patients received asfotase alfa with dose of 2 mg/kg three times weekly subcutaneously. All patients survived and the radiographic findings, laboratory findings, developmental milestones and respiratory function were improved. Injection site reactions were the most frequent adverse events, however, no serious adverse events were noted. Our results add support to the safety and efficacy of treatment with asfotase alfa for HPP patients. A persistently low ALP level in patients with unspecified diagnoses could be a key to diagnose HPP. Since 2020, health insurance for treatment with asfotase alfa has begun to apply for HPP patients in Korea on the condition that the treatment start and stop criteria are met. Accurate diagnosis and prompt treatment play an important role for avoiding preventable morbidity and premature mortality in patients with HPP.