Home / What is FOP? / Diagnosis

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.