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Home » Children's Health » Ultra-rare genetic disease often confused with cancer in children

Michelle Davis

Executive Director, IFOPA

FOP turns patients’ muscles and tendons into bone and is often misdiagnosed. Know the signs and how to get more information on this rare, disabling condition.

Fibrodysplasia ossificans progressiva (FOP) is one of the rarest, most disabling conditions known to medicine. With only 1,000 confirmed cases worldwide, the disease exhibits no ethnic, racial or gender patterns. FOP causes bone to form in muscles, tendons and connective tissues. Eventually, these bridges of bone restrict movement and form a second skeleton, imprisoning the body.

Signs of FOP for clinical diagnosis

Telltale signs of FOP include:

The exact rate of progression for FOP is unpredictable and varies from person to person. However, it appears symptoms in the upper body are more prevalent in childhood. Lower body symptoms tend to present during adolescence.

While the initial diagnosis is clinical, a definitive FOP diagnosis requires genetic confirmation of the ACVR1 gene mutation. It’s important to note FOP is accelerated by trauma. This includes intramuscular injections and other procedures. If FOP is suspected, all elective procedures such as surgeries, biopsies and immunisations should be deferred. Patients should be referred to genetics and/or an FOP expert.

If FOP is suspected, all elective procedures
such as surgeries, biopsies and
immunisations should be deferred.

Treating FOP patients: supporting families

FOP patients need a primary physician who is willing to collaborate with FOP experts to assemble and coordinate a local care team. The International FOP Association (IFOPA) was formed in 1988 by a woman with FOP and can assist healthcare providers.

The IFOPA also offers healthcare professionals access to FOP Treatment Guidelines and Covid-19 resources essential for FOP patients who often have restricted lung capacity.

International network of FOP expertise

The International Clinical Council on FOP (ICC) is an autonomous and independent group of 21 internationally recognised physicians who are clinical experts in FOP from 14 nations and six continents. The ICC was established to coordinate and consolidate a global voice for the best practices for clinical care and clinical research for people who suffer from FOP.

You can connect with the ICC and other helpful resources explicitly for healthcare providers caring for patients with FOP at

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