| Summary: | Hypophosphatasia (HPP) is a genetic disorder causing loss of function of tissue-nonspecific alkaline phosphatase (TNSALP) enzyme, which is necessary for bone mineralization. Clinically, the manifestation of this disease is variable; the severity of the presentation is largely determined by the age of the onset of symptoms: the earlier the onset, the more severe the condition.1-3 In its most severe presentation, infants affected by the disease die in utero or shortly after birth, while patients who manifest HPP as infants (i.e., within six months after birth) would have severe presentation, with irreversible bone deformities, rachitic chest changes affecting respiratory functions, and exhibiting an overall one-year survival rate of around 50%.1-5 In the mildest presentation, patients suffer from teeth loss with little or no other skeletal manifestation.1-3,5 The incidence of the prenatal and infantile forms of HPP in Canada is estimated to be 1:100,000 live births.6 The incidence is much higher within the Canadian Mennonite population; it has been reported to be one in every 2,500 births in Manitoba.7,8 Currently, except for asfotase alfa (Strensiq), there are no approved treatments for HPP. The main stream of therapy focuses on supportive care, including respiratory support, orthopedic surgery, physiotherapy, a low calcium diet, pain relief, and dental care. Asfotase alfa is a therapeutic protein that acts in place of the defective endogenous TNSALP enzyme.9
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