X-linked hypophosphatemic rickets (XLHR) is a life-long phosphate waste disorder that presents in early childhood with lower limb deformities, stunted growth, and bone and joint pain. In adults, osteomalacia and fractures may develop, aggravating bone and joint pain, stiffness, and disability. A 50-year-old woman with XLHR was referred to Rheumatology for incapacitating pain in her left lower limb with gait impairment. A pseudofracture was identified in the radiography of long bones, and secondary hyperparathyroidism was also observed. Treatment was optimized, and marked clinical improvement occurred. The authors review and discuss the underlying pathophysiology of this disease and its adequate management.