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Internal Medicine

Training Level

Resident PGY 3


Henry Ford Hospital


Introduction: Hypophosphatasia (HPP) is a rare inherited disorder of the ALPL gene which leads to decreased alkaline phosphatase (ALP) activity. Though severe symptoms are seen in childhood, adult HPP is milder and often asymptomatic except for low bone density, thus frequently escapes diagnosis. Hallmarks of adult HPP include decreased ALP, non-traumatic fractures or pseudo-fractures, and premature loss of teeth.

Case: A 56 year old previously healthy man presented for evaluation of bilateral atypical femur fractures. He experienced a soft impact slip-and-fall in September 2019 sustaining left mid-shaft displaced femur fracture. Twelve weeks later he stepped oddly while walking and felt pain in right his thigh resulting in fall; x-ray showed a non-traumatic, mid-shaft non-displaced transverse right femur fracture. He had no prior history of fractures, osteoporosis, bisphosphonate use, or any predisposing factors for osteoporosis. On review of laboratory results, it was noted that he had decreased levels of ALP for at least 9 years. After the two recent fractures, his ALP was inappropriately low-normal.

Discussion: Review of the literature suggests that initial presenting symptoms of adult HPP are usually bone pain related to pseudo-fractures or premature loss of teeth. Atypical femur fractures (AFF) have been reported in the setting of previously undiagnosed HPP and concurrent bisphosphonate therapy, which is a known independent risk factor for AFF. However, our case is unusual in that bilateral AFF were the only presenting manifestations of an underlying undiagnosed adult onset HPP in an otherwise healthy individual not taking bisphosphonates.

Presentation Date


Bilateral Atypical Femur Fractures as a Presenting Manifestation of Unrecognized Hypophosphatasia