Diagnosing FOP

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Due to its rarity, FOP is commonly misdiagnosed.  Many doctors and medical professionals have never heard of the condition.

Where a diagnosis of FOP is suspected,

no further treatments or test should be carried out before seeking expert medical advice.

The ‘FOP’ toes, combined with unexplained swellings across the body, are a strong indicator of FOP.

Key symptoms of FOP:

‘FOP’ toes

People with FOP appear normal at birth, except for the tell-tale malformed, turned-in big toes.  The big toes may be shortened and/or curl under.  In some instances, the great toes may be missing completely.  The person may also have shorter or turned in thumbs.


The swellings are known as flareups.  These are painful lumps that can appear anywhere across the body.  They can be red and inflamed.  They can last from a few weeks to a few months.  At the very least they cause inconvenience and discomfort; at worst they are excruciatingly painful.  They are often misdiagnosed as tumours.

A flare-up can appear spontaneously or after an incident.  As the flare-up subsides, new bone growth may have occurred.

Restricted movement

People with FOP suffer from stiffness in joints. Some may be present at birth, other stiffness may develop over time.  Babies with FOP rarely crawl due to fused joints in the neck or malformed joints.

Sadly, misdiagnosis is common

The toes are often thought to be bunions or hallux valgus, while the swellings can be misdiagnosed as cancer.  Often, patients are subjected to unnecessary and potentially harmful investigative procedures and treatments.  Some medical professionals may try to ‘straighten’ or ‘correct’ the toes.  Until a diagnosis of FOP is confirmed or disproved through a genetic test, no further treatments should be undertaken.  This is critical to reduce the likelihood of FOP fall-out from such procedures in the event that the patient’s diagnosis proves conclusive for FOP.

If you suspect a diagnosis of FOP, do not permit any biopsies of the area and seek expert FOP specialist advice.

Due to the rarity of FOP, most GPs and other medical professionals will not have heard of the condition.

Direct your healthcare professional to the International Clinical Council for FOP’s Medical Guidelines.

For specialist FOP advice contact:

Professor Richard Keen rno-tr.metabolicsecretary@nhs.net RNOH

Professor Fred Kaplan Frederick.Kaplan@uphs.upenn.edu 

Professor Robert Pignolo Pignolo.robert@mayo.edu 

Or contact FOP Friends for further guidance.

FOP: Recognition, Treatment and Hope

A continuing professional development tool for healthcare professionals

Springer Healthcare, in collaboration with global FOP specialists, have developed a learning program to educate and assist healthcare professionals navigate the challenges of diagnosing a person with FOP. There are follow-up videos and resources with further information to support professionals to provide medical care for those diagnoses and living with FOP.

A good starting point is the quiz.

Can you spot FOP? Click here to start

A gallery of FOP toes

A selection of photos of FOP toes, illustrating the different ways FOP may present.  There are photos from babies through to adults, along with two x-rays which illustrate the missing joint in the great toe.

Watch now

Further reading

For a more detailed explanation of FOP, please read the first two chapters of ‘What is FOP? A guidebook for families’.

Read now

The Medical Management of Fibrodysplasia Ossificans Progressiva: Current treatment considerations

The International Clinical Council for FOP is a group of global FOP specialists whose mission is to educate and advise on the best practices and care for those living with FOP.

They have written a set of medical guidelines for healthcare professionals to assist them in providing the best possible care for their patient with FOP.  These are updated when there are changes to guidance.  This is especially relevant at the moment as we are learning to live with Covid.

All medical professionals who are caring for a patient with FOP should familiarise themselves with these guidelines, and also revisit them regularly to ensure they are familiar with any changes to best practice.

Visit the ICC for FOP’s Website