Fibrodysplasia ossificans progressiva (FOP) often begins in the neck and shoulders and progresses along the back, trunk, and limbs of the body.
In addition, malformed big toes (short, bent, and sometimes curved inward) are always associated with the condition and can be observed at birth. While the toe malformations cause few problems, they serve as an important early sign of FOP before the onset of extra bone.
Rather than crawl on their hands and knees, most kids with FOP scoot on their buttocks; then get up and walk. The reason that most cannot crawl is because the facet joints in the back of the neck have not formed properly or have fused, thus limiting movement.
Although FOP is congenital, meaning that FOP starts before birth, the extra bone does not form before birth.
Symptoms of FOP, including bone formation, usually begin during the first two decades of life.
The majority of affected people learn that they have FOP before the age of ten. Inflamed (and sometimes painful) swellings, typically in the shoulder and back areas and sometimes on the scalp or head, are usually the first sign of FOP. The swellings eventually clear up, but they leave behind a new piece of mature bone.
People who have FOP experience different rates of new bone formation. In some the progress is rapid, while in others it is more gradual. In each case, the exact rate of progression is unpredictable, although there appears to be a pattern to the progression.
For example, extra bone formation tends to occur in the neck, shoulders, and upper back early in life and in the hips and knees during adolescence or early adulthood.
Toes of infant with FOP:
Toes of adult with FOP:
More on FOP symptoms and misdiagnosis:
- (PDF page 2 shows Flare-ups)
- FOP Misdiagnosis (webpage on IFOPA.org)
- Chapter 1 of "What is FOP? A Guidebook for Families" (PDF)