Prevalence and natural history of gibbus deformity in patients with Hurler syndrome

Introduction: Gibbus deformity has been documented as a common musculoskeletal abnormality in mucopolysaccharidosis type I (Hurler syndrome, MPS IH), and its recognition often leads to the diagnosis of MPS IH. While the incidence has been described, the progression of gibbus deformities is not well known. Here we describe the natural history of gibbus deformity in a single center patient population using serial spinal MRI scans. Methods: All spinal MRI scans in MPS IH patients were retrospectively reviewed. The presence, spinal location, and angulation of the gibbus deformities were collected. The angles between the superior endplate of the superior normal vertebral body and the inferior endplate of the inferior normal vertebral body were measured. Results: 24 of 47 patients (51%) were found to have cervico-thoracic deformity on their cervical MRI scans, and 19 of those 24 (79%) patients were found to have progressive cervico-thoracic deformity with average change of angle of 17.1 degrees [range 3.9, 62.8] over 5.3 years. 7 of 8 patients who had thoraco-lumbar MRI were found to have thoraco-lumbar deformity, and 4 of those 7 patients (57%) were found to have progressive thoraco-lumbar deformity with the average increase angle of 16.7 degrees [range 3.3, 47.1] over an average of 4.1 years. Conclusion: We found out that baseline spinal measurement cannot reliably predict the progression as multiple patients with normal alignment eventually developed severe deformity, whereases patients with severe deformity did not progress to require surgical intervention.