What mutation causes FOP and how does it drive ossification?

Gain-of-function ACVR1/ALK2 mutation (R206H in 97% of patients) causes hypersensitivity to BMP signaling, converting skeletal muscle, tendons, and ligaments into heterotopic bone through endochondral ossification.

What procedures should NEVER be performed in FOP?

IM injections, dental blocks, nerve blocks, biopsies, and surgical removal of HO are absolutely contraindicated as they trigger massive new ossification; emergency airway management must use nasal fiberoptic intubation.

What is palovarotene for FOP?

Palovarotene (Sohonos) is a retinoic acid receptor gamma agonist approved for FOP in 2023; reduces new HO formation during flares; flare-based dosing 20 mg/day for 4 weeks then 10 mg for 8 weeks.

What is the typical disease progression of FOP?

Typically begins in childhood (median age 3) starting at neck/shoulders/back; flare-based ossification is progressive and cumulative; most patients are wheelchair-dependent by age 30; chest wall ossification causes respiratory failure.

What childhood toe finding suggests FOP before first flare?

Hallux valgus (short great toe with malformed distal phalanx) is present at birth in virtually all FOP patients and is a pathognomonic clinical feature; recognized before the first ossification flare occurs.

Fibrodysplasia Ossificans Progressiva (FOP) Flare Severity Score

Assesses FOP episodic flare severity using warmth, swelling, pain, and ROM restriction, estimates new heterotopic ossification volume from MRI, and guides palovarotene dosing for flare prevention.

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Fibrodysplasia Ossificans Progressiva (FOP) Flare Severity Score

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Frequently Asked Questions

What mutation causes FOP and how does it drive ossification?

What procedures should NEVER be performed in FOP?

What is palovarotene for FOP?

What is the typical disease progression of FOP?

What childhood toe finding suggests FOP before first flare?