Romosozumab-aqqg in the Treatment of Osteoporosis in a Patient With Hypophosphatasia

Hypophosphatasia is a rare, inherited condition that causes osteomalacia and recurrent fractures. Therapeutic options for osteoporosis in patients with hypophosphatasia are limited because of concerns for a greater likelihood of atypical femoral fractures with antiresorptive agents. We report here the case of a patient with hypophosphatasia and osteoporosis who was treated with romosozumab-aqqg (Romo). An 81-year-old woman presented for management of osteoporosis with multiple fractures. She experienced a decline in bone mineral density over 20 years despite sequential osteoporosis treatment with oral bisphosphonates, hormone replacement therapy, teriparatide, and denosumab. Hypophosphatasia was suspected because of low serum alkaline phosphatase levels and was confirmed by genetic testing. After diagnosing hypophosphatasia, bone mineral density continued to decline and a trial of Romo was begun. After 1 year of Romo therapy, bone mineral density improved by 21%, and 10% at the lumbar spine and total hip, respectively. These changes were substantially greater than what she had experienced with prior teriparatide therapy. Blood alkaline phosphatase remained low on Romo. To our knowledge, this is the first report of a patient with hypophosphatasia and osteoporosis treated with Romo. In our patient, Romo did not significantly impact serum alkaline phosphatase, but improved bone mineral density significantly. In conclusion, Romo is a potential treatment option for osteoporosis in patients with hypophosphatasia for whom limited alternatives exist.