This site is intended for US Healthcare Professionals only.
This site is intended for US Healthcare Professionals only.

clinical features

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.

Bilateral Malformation of the Great Toes

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.

Learn more about the characteristic malformation of the great toes here > 

fop toes


Flare-Ups – Soft Tissue Swellings that Often Signal Bone Formation

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.

More on disease management here >

Toes and Swellings: Think FOP

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

Learn more about the importance of early diagnosis here. 


  1. Pignolo RJ et al, Orphanet J Rare Dis (2011).




Heterotopic Ossification (HO) in FOP

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.

Other Clinical Features of FOP

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


  1.  Levy CE, Lash AT, Janoff HB, Kaplan FS. Conductive hearing loss in individuals with fibrodysplasia ossificans progressiva. Am J Audiol. 1999;8:29–33.
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Please always consult a healthcare professional if you require healthcare advice or if you have any specific concerns regarding Fibrodysplasia Ossificans Progressiva. The information provided here is not intended to replace professional advice. This website has been developed by Ipsen in collaboration with those living with Fibrodysplasia Ossificans Progressiva and the healthcare professionals who care for them. Ipsen would like to thank everyone for their valuable insights and stories. All names used on this website are not necessarily real names. Visit our website for more information about us, or to contact us directly. Website design and development by Kanga Health Ltd. Website reference NON-US-002031 December 2020