A person with FOP will appear healthy at birth with the exception of bilateral malformation of the great toes, which is present almost universally in those with FOP . The two great toes are typically
shortened and bent inwards, resembling a bunion. An X-ray may reveal monophalangism.
The malformation itself typically does not affect walking, and the sign is often dismissed. Early childhood years may be typical and active, although often with impaired neck movement.
By itself, this bilateral malformation of the great toes is not pathognomonic for FOP; however, presence of heterotopic bone along with bilateral hallux valgus would most likely suggest a diagnosis of FOP. Patients exhibiting these signs should be further evaluated for the disease.
Identifying clusters of signs and symptoms, especially bilateral malformation of the great toes and episodic soft tissue swellings, can speed diagnosis.