Symptoms Fibrodysplasia Ossificans Progressiva (FOP)

The formation of bony bars is usually first noticed in early childhood as a series of hard lumps in the neck or along the spine.

These lumps, which may be tender, gradually shrink in size as the affected muscles are replaced by bone. The appearance of bony lumps in muscles is usually spontaneous but can also be provoked by any injury to the muscles. Disability in FOP is physical and very variable in extent; intelligence in unaffected.

How does the condition progress?

FOP is progressive in that more muscles become involved with increasing age, but the rate of progression is very variable from one person to another. Furthermore the condition tends to show long periods of inactivity (of up to several years in length).

Can any muscles be affected?

Certain muscles are never involved in this disease. These include the muscles of the eyes, the face, the tongue, the gullet, the intestines and the muscles of continence (bowel and bladder control). The heart is never involved in this condition. Chest expansion may be reduced in FOP but the diaphragm, which is the single most important breathing muscle, is never involved.

Are there any other features of FOP?

Most people affected by FOP have some abnormalities of the fingers or toes. The big toes are most commonly involved and are usually shortened and deviated. These changes to the big toes are usually apparent at birth.