We report the case of a 45-year-old woman who presented with a six-year history of diffuse polyarthralgia responsible for major disability. She reported bilateral symmetric arthralgia in nearly every joint, as well as back pain. Muscle wasting predominating in the roots of the limbs was found. Laboratory tests showed hypocalcemia, severe hypophosphatemia, hypokalemia, alkaline phosphatase elevation, aminoaciduria, and hyperphosphaturia, with no glycosuria. Radiographs disclosed osteolysis of the pubic symphysis, multiple pelvic fractures, vertebral compression fractures, and diffuse demineralization. A bone scan visualized symmetric foci of hyperactivity in nearly all joints and fracture sites. Dramatic improvements in clinical and radiographic abnormalities were noted after six months of treatment with phosphate and calcitriol. This is a case of incomplete Fanconi syndrome, with no glycosuria. The clinical presentation of Fanconi syndrome can be misleading. Fanconi syndrome should be borne in mind as a possible cause of polyarthralgia to avoid diagnostic delay, which in our patient led to a picture of pseudomyopathy with multiple fractures.