Adult hypophosphatasia manifests in a marathon runner

A 49-year-old woman, previously healthy, presented with recurrent fractures provoked by minimal trauma. She had sustained seven fractures over the previous 2 years. While she was an avid runner, her injuries were determined to be out of proportion to the degree of trauma. Initial evaluation, exploring the more common causes such as low bone density and abnormal vitamin D metabolism, was unremarkable. On repeat of the some of the tests, a low alkaline phosphatase (AP) was noted, which raised suspicion for hypophosphatasia (HPP), a rare cause of recurrent fractures. Subsequent workup revealed a low bone-specific AP and elevated vitamin B₆ Subsequently, genetic testing confirmed the diagnosis of adult-onset HPP caused by a heterozygous mutation c.407G>A in the ALPL gene. Asfotase alfa was started; however, the patient developed an allergic reaction leading to the discontinuation of the drug.