Pamidronate Treatment of a Patient with Opsismodysplasia and a Novel INPPL1 Variant: Efficacy, Mechanism, and Clinical Outcomes.

INTRODUCTION: Opsismodysplasia (OPS) is a rare skeletal dysplasia characterized by delayed bone maturation, distinctive skeletal deformities, and severe growth impairment. Mutations in the INPPL1 gene, particularly homozygous variants, are the primary genetic cause of this condition. While bisphosphonate therapy has shown efficacy in OPS cases with hypophosphatemic rickets, its role in cases without this complication remains unclear.

CASE PRESENTATION: A 2-year-and-2-month-old girl with OPS was treated with intravenous pamidronate (0.5 mg/kg/3 months). Initial evaluations showed severe short stature and low bone mineral density (DEXA SDS: -3.16). After three courses of treatment, the patient achieved independent walking, and her DEXA SDS improved to -2.5 over 1 year.

DISCUSSION: Pamidronate is effective in treating OPS even in the absence of hypophosphatemic rickets, showing potential as a therapeutic option for this rare condition.