Background: Hypophosphatasia (HPP) is a rare inborn error of metabolism that results from dysfunction of the tissue non-specific alkaline phosphatase enzyme. Its manifestations are extremely variable, ranging from early lethality to disease limited to the dentition. The disease is life-threatening when manifesting within the first six months of life, excepting the extremely rare benign perinatal hypophosphatasia. Childhood hypophosphatasia, defined as onset of symptoms between six months and eighteen years, can manifest as rickets, pain, decreased mobility, deficits of growth, and fractures. Historical treatment has generally involved a combination of dietary and rehabilitative interventions.
Main document: Asfotase alfa (Strensiq™), is a first-in-class bone-targeted recombinant tissue nonspecific alkaline phosphatase which has shown significant improvements in morbidity and mortality in patients with perinatal and infantile hypophosphatasia. Subsequent research has also shown improvements in morbidity for patients with childhood hypophosphatasia as measured by improvement in rickets, growth, strength, mobility, and quality of life. This enzyme replacement therapy has generally been well-tolerated, with most adverse reactions being mild-to-moderate in nature. The author shares their approach to decisions on commencement of ERT based from experience of managing approximately fifteen patients across the age spectrum. This approach focuses on assessing the severity of five key manifestations of childhood HPP: decreased mobility, pain, rickets, deficits of growth, and fractures.
Keywords: Alkaline phosphatase; Asfotase alfa; Brittle bone disease; Enzyme replacement therapy; Hypophosphatasia; Rare bone disease; Rickets.