Acquired Osteomalacia Associated with Autoantibodies against PHEX

This study identified autoantibodies against PHEX (phosphate-regulating endopeptidase Xlinked) in patients with unexplained acquired fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets osteomalacia (FGF23rHR). Among 13 patients with suspected tumor-induced osteomalacia but no detectable tumors, 5 (38%) tested positive for PHEX autoantibodies. The findings suggest a novel autoimmune mechanism for osteomalacia, potentially reducing unnecessary tumor-detection procedures and enabling targeted therapies like burosumab or immunomodulatory treatments.

This study identified autoantibodies against PHEX (phosphate-regulating endopeptidase Xlinked) in patients with unexplained acquired fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets osteomalacia (FGF23rHR). Among 13 patients with suspected tumor-induced osteomalacia but no detectable tumors, 5 (38%) tested positive for PHEX autoantibodies. The findings suggest a novel autoimmune mechanism for osteomalacia, potentially reducing unnecessary tumor-detection procedures and enabling targeted therapies like burosumab or immunomodulatory treatments.