Not Your Typical Bisphosphonate Intolerance: A Case of Unusual Bone Pain With Low Alkaline Phosphatase.

Bisphosphonates, first-line medications for osteoporosis, are often not tolerated or discontinued for multiple reasons. Hypophosphatasia (HPP) is a genetic deficiency with the enzyme activity of tissue-nonspecific alkaline phosphatase (TNSALP). The symptoms of adult HPP are often non-specific, and the diagnosis may be delayed for years. Low serum alkaline phosphatase, a hallmark feature of HPP, is often overlooked. Genetic testing is recommended to confirm diagnosis, and treatment with asfotase alfa, a recombinant alkaline phosphatase, is available for patients with HPP. We report a case of HPP in a 71-year-old female with recurrent skeletal pain and bisphosphonate intolerance who ultimately was diagnosed with HPP.