Supplementary Material for: 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 caused by homozygous variant in the INPPL1 gene (c.1976C>T; p.Pro659Leu) gene mutations, characterized by delayed bone maturation and specific skeletal deformities. While bisphosphonate therapy has been effective in OPS with hypophosphatemic rickets, its use in OPS without this complication is less documented. 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 one year. Discussion/Conclusion: Pamidronate is effective in treating OPS even in the absence of hypophosphatemic rickets, showing potential as a therapeutic option for this rare condition.