Fibrodysplasia ossificans progressiva
Fibrodysplasia ossificans progressiva
Also known as:FOP, myositis ossificans progressiva, ACVR1-related heterotopic ossification, China Second Rare Disease Catalog item 28
Fibrodysplasia ossificans progressiva is a rare ACVR1-related connective tissue disorder in which soft tissues gradually form extra bone after painful flare-ups, limiting movement over time.
Start Here
A quick guide to the next step: which department to start with, what to prepare, and what to ask.
A child with malformed big toes and recurrent soft-tissue lumps or stiffness should see an FOP-aware orthopedic, pediatric orthopedic, or genetics team. Avoid unnecessary biopsy, surgery, and intramuscular injections when FOP is suspected.
The classic clue is malformed big toes at birth, followed in childhood by painful swelling of the neck, shoulders, back, or limbs that later turns into heterotopic bone. Trauma, injections, surgery, biopsy, and viral illness can trigger flare-ups.
Management focuses on avoiding trauma, treating flare-ups, preserving function, and protecting breathing. Palovarotene is approved in some countries for reducing new heterotopic ossification in eligible patients, but age limits, risks, and access require specialist review.
FOP is usually caused by a new ACVR1 variant and follows an autosomal dominant mechanism. A small number of cases are inherited, so genetic counseling is still important.
Early lumps can be mistaken for cancer, hemangioma, fibromatosis, dermatomyositis, or post-traumatic hematoma. Biopsy or surgery can worsen ossification.
This page helps patients and families organize care leads. It does not replace a clinician’s diagnosis or treatment plan. For testing, medication, referrals, emergency care, and support applications, follow qualified clinicians, medical institutions, support organizations, and official sources.
Diagnosis Path
Organized around the practical patient journey: identify clues, avoid common delays, then prepare for care.
When to Suspect It
- Malformed, short, bent, or deviated big toes are present at birth or in infancy.
- A child develops recurrent painful soft-tissue swelling in the neck, back, shoulders, trunk, or limbs followed by hardening and loss of movement.
- Stiffness or new bone formation worsens after minor falls, intramuscular injections, dental procedures, or infections.
- Imaging shows heterotopic ossification without a better explanation such as major trauma, cancer, or infection.
Common Wrong Turns
- Biopsying or removing early lumps as if they were tumors, which can trigger more bone formation.
- Treating it as routine myositis, hematoma, or fibromatosis without checking the toes and ACVR1.
- Using intramuscular injections, deep massage, forceful stretching, or high-risk procedures unnecessarily.
- Focusing only on imaging and missing airway, dental, vaccination, fall-prevention, and home-adaptation planning.
Departments to Start With
- Orthopedics
- Pediatric orthopedics
- Medical genetics
- Rehabilitation medicine
Before the Visit
- Photograph toe, thumb, or skeletal findings and keep a timeline of each swelling flare-up.
- Bring X-ray, CT, MRI, ultrasound, surgery, and biopsy records; state clearly that FOP is suspected to avoid repeat biopsy.
- List triggers such as falls, injections, surgery, dental work, viral illness, and vaccination route.
- Track jaw opening, swallowing, breathing, sleep, falls, pain, and daily function.
Tests to Ask About
- ACVR1 genetic testing, especially when the clinical picture is typical but molecular confirmation is needed.
- Low-trauma imaging to assess heterotopic ossification; avoid invasive tissue sampling for diagnosis when possible.
- Pulmonary function, spine and chest-wall mobility, nutrition, and dental assessment when jaw or chest mobility is limited.
- A written flare-up plan, pain plan, vaccination route guidance, and anesthesia or airway precautions.
Questions for the Doctor
- Does this pattern fit FOP, and what tests can confirm it without causing trauma?
- What should we do during a flare-up, and which procedures should be avoided?
- Is palovarotene or a clinical trial relevant for me, and what are the risks and access issues?
- How should dental care, vaccines, fall prevention, school or work adaptations, and emergency airway planning be handled?
Basic Information
Medical Notes
More complete medical explanations are kept here for discussion with clinicians.
Symptoms
FOP often begins with congenital malformation of the big toes. In childhood, painful soft-tissue swelling or flare-ups can occur in the neck, back, shoulders, trunk, or limbs, followed by hardening and heterotopic bone that limits joint movement.
Over time, jaw opening, eating, speech, spine and chest-wall movement, mobility, pain, and breathing can be affected. Trauma, surgery, biopsy, intramuscular injections, and infections can trigger or worsen flare-ups.
Diagnosis
Typical FOP is confirmed by congenital big-toe malformation, progressive heterotopic ossification, and an ACVR1 pathogenic variant. In many cases, clinical clues are strong enough that the priority is avoiding biopsy or excision done for diagnosis.
Differential diagnosis includes cancer, aggressive fibromatosis, dermatomyositis, traumatic myositis ossificans, hematoma, and vascular malformation. Suspected FOP should be referred to an experienced center.
Treatment
First-line management is prevention: avoid unnecessary surgery, biopsy, intramuscular injections, forceful rehabilitation, and high-risk trauma. During flare-ups, clinicians may use short-term anti-inflammatory or pain-control strategies to reduce pain and protect function.
Palovarotene is FDA-approved for eligible patients of specific ages to reduce the volume of new heterotopic ossification, but it has important risks including embryo-fetal toxicity and premature epiphyseal closure in growing children. Use requires FOP-specialist evaluation.
Long-term Care
Long-term care includes fall prevention, low-trauma movement and positioning, pulmonary and chest-wall monitoring, nutrition, dental planning, pain care, mental health support, and home, school, or work adaptations. Any surgery, anesthesia, or dental procedure needs advance planning to minimize trauma.
Fertility and Family
Most FOP is caused by a new ACVR1 variant, but the inheritance mechanism is autosomal dominant. People with FOP who are planning pregnancy should discuss genetic risk, pregnancy risk, medication teratogenicity, delivery, and anesthesia planning.
When to Seek Urgent Care
Seek urgent care for breathing difficulty, severe chest or neck restriction, marked swallowing difficulty, severe pain or rapid loss of function after a fall, high fever with severe flare-up, suspected airway problems, or any need for emergency surgery or anesthesia.
Prognosis
FOP usually progresses over time. Early recognition and trauma avoidance can reduce preventable ossification and function loss, while respiratory, nutrition, dental, and adaptation planning shape quality of life.