The enthesopathic changes of hypophosphatemic osteomalacia in adults: radiologic findings

The enthesopathy (bone proliferation at sites of ligament, tendon, joint capsule, and interosseous membrane attachment) that may be present in adults who have longstanding hypophosphatemic osteomalacia, the most common type of osteomalacia, has received little attention in the radiologic literature. These proliferative enthetic changes may be associated with various musculoskeletal symptoms. The spectrum of proliferative enthesopathic changes, involving the axial and appendicular skeleton, is described in six patients 18-63 years old. Proliferative changes at the attachment of the annulus fibrosus were present in six of six patients and ranged in extent from tiny hyperostoses at a few levels to thin marginal symmetric syndesmophytes involving the entire lumbosacral spine and mimicking spondylitis. Thoracic spinal syndesmophytes were present in four patients and cervical hyperostoses of various magnitudes were present in three patients. Changes in the sacroiliac joints were present in four of six patients and varied from mild widening to symmetric intraarticular and anterior paraarticular bony bridging. Proliferative enthesopathy involving the pelvis and proximal femora was present in six of six patients. Appendicular changes included accessory ossicles within the wrist and hands and bony proliferation of the distal radius and metacarpal heads. These were noted in four patients. Ossification of the interosseous membrane of the forearms or the lower extremities was present in six patients and paraarticular bony proliferation about the elbows was noted in four patients. It is apparent that the severity of the enthesopathy that occurs may vary, and that hypophosphatemic osteomalacia should be recognized as a cause of enthesopathy even if other radiographic findings of osteomalacia may not be present on available radiographs.