Fibrodysplasia Ossificans Progressiva: Clinicoradiological Insights Into a Rare Case.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterised by progressive heterotopic ossification of soft tissues due to mutations in the ACVR1 gene, leading to dysregulated bone morphogenetic protein signalling. Over time, recurrent episodes of painful inflammatory soft tissue swellings (flare-ups) lead to progressive ossification and eventual ankylosis of joints, resulting in severe restriction of mobility. Most patients become wheelchair-bound by the third decade and may succumb to complications such as thoracic insufficiency syndrome and cardiorespiratory compromise. Due to its rarity and lack of awareness, FOP is often misdiagnosed, and patients may undergo unnecessary invasive procedures such as biopsies or surgical excisions, which can precipitate rapid disease progression. Early recognition based on clinical and radiological findings is therefore critical to prevent iatrogenic harm. We present a rare case of a six-year-old girl with this condition, emphasising the diagnostic challenges and key imaging findings.