Paravertebral ligament ossification in vitamin D-resistant rickets: incidence, clinical significance, and genetic evaluation

A retrospective observational study. The objective of this study was to analyze the cases of paravertebral ossification in vitamin D-resistant rickets (VDRR) and elucidate its incidence and clinical significance, and report specific genetic mutations uniquely associated with this phenomenon. Paravertebral ligament ossification has been described in VDRR in a few cases previously. However, supraspinous and interspinous ligament ossification has so far not been described to occur in association with VDRR. We reviewed 6 cases of paravertebral ligament ossification with the added feature of supraspinous and interspinous ligament calcification. Forty-four patients with clinical, radiological, and biochemical diagnoses of VDRR, who were positive for mutations in the PHEX gene, were screened for the presence of paravertebral ossification with plain radiographs and computed tomography/magnetic resonance imaging if necessary. This was correlated with the severity of disease, and we looked for specific genetic mutations. Six patients had paravertebral ligament ossification, which included supraspinous and interspinous ligament ossification. These patients had a more severe systemic disease, with all patients requiring at least 1 surgery for deformity correction of the limbs, with a total of 10 surgical procedures performed in these 6 patients. c.1601C>T, c.1699C>T, c.1363G>T, and c.466_467insAC were the genetic mutations associated with these cases. The spinal changes with paravertebral ligament ossification in VDRR were described in this study. Four different gene mutations related to the PHEX gene were detected in them. The presence of these changes was suggestive of a more severe systemic disease.