A Rare Presentation of Non-Traumatic Recurring Bone Fractures in Adult Patient With Juvenile Onset Hypophosphatasia

Abstract

Background: Hypophosphatasia is a rare metabolic bone disease caused by mutations in the tissue-nonspecific alkaline (TNSALP) phosphatase gene. The disease is typically diagnosed in children but may be seen in adults with premature loss of adult teeth, poor bone healing, recurrent bone fractures, and limited mobility due to chronic pain. Clinical case: A 48-year-old female with Juvenile Onset hypophosphatasia and diabetes mellitus type 2 who presented to the endocrine clinic for diabetes mellitus. She had a telemedicine visit because she was not able to come to the office due to her recent rib fracture and pain. She had multiple fractures since she was 16-years-old with multiple fractures in her toes. She later developed a femur fracture when 20 years old and second at 28-years-old in the other femur. She was tested for juvenile hypophosphatasia and the diagnosis was confirmed. She received no treatment at that time. She subsequently had recurrent non-traumatic rib fractures that interfered with daily life. She is unable to exercise due to her frequent fractures and consequently having poor diabetic control. She has family history of brother with femur fracture. Labs showed decreased alkaline phosphatase (<5 normal: 38–126 U/L), elevated vitamin B6 levels (2296.2: normal 20–125 nmol/L) normal vitamin D (33: normal 30–100 ng/mL) and calcium levels. Chest x-ray showed multiple rib fractures with different healing stages. Dexa scan was also done and was normal to age with lowest Z-score being 8.2. Patient was started on Asfotase Alfa (an enzyme replacement therapy that contains the active site of TNSALP). Conclusion: This case illustrates the debilitating effects of hypophosphatasia and importance of recognizing previously untreated adult patients with hypophosphatasia. Many patients have very late diagnosis and suffer severe complications in their adulthood. Although this disease is rare, recognizing the symptoms of juvenile onset hypophosphatasia can help initiate early treatment to decrease these complications. Hypophosphatasia should be considered as a differential diagnosis in adults with multiple fractures and decreased alkaline phosphatase.