Case Report: Atypical femoral fractures in adult-onset hypophosphatasia treated with low-dose asfotase alfa and adjunctive teriparatide therapy.
Yoon-Sok Chung, Kwang-Kyoun Kim, Gokul B S et al.
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Case in brief
A 52-year-old woman presented with progressive pain and bilateral atypical femoral fractures. Low alkaline phosphatase, markedly elevated pyridoxal 5'-phosphate, prior metatarsal fracture, premature tooth loss, and pathogenic ALPL variants supported adult-onset hypophosphatasia. Low-dose asfotase alfa was followed by callus formation and pain improvement, but pain later recurred with radiographic fracture progression. Staged intramedullary fixation was complicated by two perioperative femoral fractures. Teriparatide was added while asfotase alfa continued; at 5-year follow-up, all femoral fractures had united, and she was ambulatory without assistance or fracture-related pain.
What made this case unusual
The case combined bilateral atypical femoral fractures with adult-onset hypophosphatasia and two perioperative femoral fractures during staged fixation, highlighting the complexity of surgical management in this setting.
Diagnostic / clinical pearl
In an adult with atypical femoral fractures, low alkaline phosphatase alongside elevated pyridoxal 5'-phosphate, relevant fracture or dental history, and pathogenic ALPL variants can support hypophosphatasia as the underlying diagnosis.
Why it matters
The course illustrates that fracture healing may remain inadequate despite low-dose asfotase alfa, and that management may require individualized medical and surgical approaches with ongoing radiographic follow-up.