Efficacy of asfotase alfa in a patient with adult-onset hypophosphatasia without obvious bone lesions: a case report with review of literature

Abstract

The use of asfotase alfa, a bone-targeted recombinant alkaline phosphatase (ALP) enzyme, for the treatment of adult-onset hypophosphatasia (HPP) remains controversial, particularly in patients without evident bone abnormalities. We report the case of a 41-year-old woman with a history of Graves’ disease, who presented with progressive joint pain and severe fatigue. Despite the absence of bone lesions, the patient was diagnosed with HPP based on persistently low alkaline phosphatase levels, family history, and a novel heterozygous ALPL variant (p.Ala205Thr). Functional analysis revealed a dominant-negative effect for this variant. Her symptoms significantly interfered with her daily activities owing to uncontrolled pain and loss of motor function and were so exacerbated that high doses of acetaminophen and NSAIDs were ineffective. Treatment with asfotase alfa was initiated based on multidisciplinary team consensus. Within 3 months of treatment initiation, her pain improved significantly, as indicated by reduced scores on the visual analog scale from 6.6 to 0.9, and elimination of the need for analgesics. Additionally, her grip strength increased, and her urinary phosphoethanolamine levels and serum pyridoxal 5'-phosphate/pyridoxal ratio decreased from 90.4 to 57.8 μmol/g·creatinine and from 4.6 to 0.4, respectively. These improvements have been maintained for more than 2 years. This case highlights the potential of asfotase alfa in effectively alleviating symptoms in patients with adult-onset HPP without bone lesions, emphasizing the importance of patient selection and outcome monitoring. We also discuss the key considerations for future treatment, supported by a literature review of asfotase alfa in adult patients with HPP.