Unmasking the Skeletal Impostor: Hypophosphatasia Masquerading as Fibromyalgia and Osteoporosis in Rheumatoid Arthritis

Summary: Hypophosphatasia (HPP) is a rare genetic disorder caused by ALPL gene mutations, leading to low alkaline phosphatase and impaired bone mineralization. This case describes a 67-year-old woman with a history of rheumatoid arthritis, osteoporosis, fibromyalgia, and recurrent fractures, ultimately diagnosed with HPP after persistent symptoms and low ALP levels. Genetic testing confirmed the diagnosis, highlighting the diagnostic challenges and overlapping features with other musculoskeletal conditions. The case emphasizes the importance of early recognition and appropriate treatment—notably avoiding bisphosphonates—while illustrating the benefits of enzyme replacement therapy for improving outcomes in HPP.