Since FOP is a progressive, severely disabling, life-shortening disease that is often misdiagnosed, early identification is important. When patients are identified and diagnosed, preventive measures and precautions can be taken to prevent iatrogenic harm.
Children with FOP appear normal at birth with the exception of a bilateral malformation of the great toes, or congenital hallux valgus. The malformed toes are typically shortened, bent inward, and resemble a bunion.
This is the most identifiable of the clinical features of FOP. the hallux valgus is also associated with the absence of a phalanx (a feature which may also be seen in the thumbs of some individuals with FOP), and is seen in nearly all patients with FOP.
Heterotopic ossification (HO) in FOP is often preceded by a flare-up. Flare-ups are episodic soft tissue swellings, which, before diagnosis, may be mistaken for tumors. These tissue swellings can increase or decrease quickly in size and can move or change shape. It is important for patients to recognize a flare-up and to seek proper management.
If you have a patient with abnormal toes as described above, and the patient has a history or presence of tumor-like soft tissue swellings, it could be FOP.1
FOP is characterized by the formation of normal bone in abnormal places. While flare-ups often signal the onset of HO, this extraskeletal bone formation can occur even in the absence of a flare-up. In FOP, skeletal muscle, tendon, and ligament tissue are replaced by bone, causing cumulative and irreversible disability.
HO formation can be unpredictable, and patients with FOP live with the uncertainty of knowing joints can become locked overnight.
In infants, scalp nodules that may change size and shape are common.
Neck stiffness may occur, as well as limited range of motion in the neck and shoulders.
Throughout life, flare-ups continue as episodic painful soft-tissue swellings on the neck, chest, or back and throughout the body.
Patients with FOP may experience skeletal anomalies that include short malformed thumbs (brachydactyly), curvature of a digit (clinodactyly), short broad femoral necks, and proximal medial tibial osteochondromas.
Progressive hearing impairment is common in FOP, occurring in approximately 50% of patients, with onset typically in childhood or adolescence. This is thought to be due to middle ear ossification; however, in some patients, the hearing impairment is neurological in nature.1