This rare disorder is characterized by physical handicap due to intermittently progressive ectopic ossification and malformed big toes which are often monophalangic. Occasional features include short thumbs, fifth finger clinodactyly, malformed cervical vertebrae, short broad femoral necks, deafness, scalp baldness, and mild mental retardation. Although most cases are sporadic, several examples of affected twins and triplets have been reported. Furthermore, dominant inheritance is supported by observations of 2 or 3 successive generations affected and the finding of a paternal age effect in sporadic cases (Tuente et al., 1967). Connor and Evans (1982) found a point prevalence of 0.61 per million in the United Kingdom and gave a direct estimate of the mutation rate of 1.8 per million gametes per generation

fibrodysplasia ossificans progressiva
autosomal dominant
progressive ossification of muscle and conective tissue
ossification of ligaments and tendons
nuchal ligament ,br> upper extremities and neck==>shoulders, back, and spine==>chest
pelvic entheses
asymptomatic at birth
90% --> short great toes
Images

Genetics Home Reference Page on this rare genetic condition

Wheeless' Textbook of Orthopaedics
may present w/ signs of localized inflammation or pain, elevated skin temp, etc.
- tends to occur after thr, spinal injury, head injury (11%), burns, bruises;

Radiology. Heterotopic ossification (HO) is the abnormal formation of true bone within extraskeletal soft tissues. Classically, many diseases sharing this common feature were lumped under the category of myositis ossificans, a term that has fallen into disfavor because primary muscle inflammation is not a necessary precursor and ossification does not always occur in muscle tissue since it frequently shows a predilection for fascia, tendons, and other mesenchymal soft tissues. The term heterotopic ossification largely has replaced myositis ossificans in the literature.

The term heterotopic ossification (HO) describes bone formation at an abnormal anatomical site, usually in soft tissue. Stover et al classify HO into the following 3 types:
Myositis ossificans progressiva (fibrodysplasia ossificans progressiva)
Traumatic myositis ossificans
Neurogenic heterotopic ossification

Heterotopic ossification (HO) following spinal cord injury (SCI) was described first by Dejerine and Ceillier in 1918 as paraosteoarthropathy. The process is one of formation of mature lamellar bone, which is indistinguishable from normal bone, in soft tissues surrounding paralyzed joints. The bone is not connected to periosteum and becomes encapsulated as it matures. The pathology is similar to that of fracture callus, except that bone forms in the connective tissue between the muscle planes. HO also is seen after other neurologic insults such as traumatic brain injury (TBI) and stroke, as well as after thermal injuries and orthopedic procedures (eg, total hip replacement). In experimental models of HO formation, ischemia and tissue expression of bone morphogenic proteins have been shown to play important roles. Bone morphogenic proteins likely act on mesenchymal stem cells present in tissue and, thus, activate them to differentiate into osteoblasts (Banovac, 2004).

Excision of Hetertopic Bone About the Elbow: - hetertopic bone is most often located along the posteromedial aspect; - medial approach to the elbow is performed along with an anterior transposition of the ulnar nerve; - careful proximal and distal exposure of the nerve is required before any attempt is made to dissect the nerve out of the hetertopic bone; - further exposure is obtained w/ osteotomy of the medial epicondyle, which can then be fixed w/ a single cannulated screw at the end of the case; - postoperatively the elbow is splinted in extension, when not undergoing supervised ROM;

Wheeless' Textbook of Orthopaedics
- typically develops on x-ray 3-8 wks postop in pericapsular area of the affected hip joint; - over all incidence is 50% (1/3 of these are clinically significant); - risk factors: - male gender (uncommon in females); - active AS; - DISH - post traumatic arthritis; - heterotrophic osteoarthritis - previous HO; - previous hip fusion; - Paget's disease - Parkinson's disease - excessive osteophytosis or enthesiopathic radiographic changes on AP of pelvis; - head injury and/or spinal cord injury;

Describes the post THR complication of heterotopic ossification

Spinal Cord Injury - InfoSheet #12 "Heterotopic Ossification"
Level -Professional Date: June, 1997
Heterotopic ossification (HO) is the development of bone in abnormal areas, usually in soft tissues. Heterotopic ossification develops most commonly in individuals who have an injury, such as spinal cord injury, that results in neurologic deficits. It is therefore referred to as neurogenic heterotopic ossification. The incidence rate of heterotopic ossification in individuals with spinal cord injury is approximately 16 to 53 percent.

may present w/ signs of localized inflammation or pain, elevated skin temp, ect. - tends to occur after thr, spinal injury, head injury (11%), burns, bruises; - Events leading to HO; - mesenchymal cell (XRT prevents induced differentiation) - osteoblast - matrix (EHDP) - osteocyte - HO following THR: - HO of the elbow: - HO following spinal cord trauma: - radiographically develops in 3-5% of patients, 1-4 mo (or upto 18 mo) after injury; - it occurs below the level of the injury, usually at major joints; - incidence is 40% (1/2 of these are clinically significant); - after transection of spinal cord, ossification often takes place in soft tissues adjacent to large joints; - lower extremities are particularly suseptible & most dramatic changes are seen in Knee> Pelvis> Hip; - characteristic finding is a bilateral accretion of well defined bone which encircle the joints;

The International FOP Association, or IFOPA, is a nonprofit support organization for families dealing with a rare genetic condition known as Fibrodysplasia Ossificans Progressiva (FOP). Simply stated, FOP causes muscles and other connective tissue to turn into bone, eventually causing immobility as FOP bone fuses joints. The IFOPA's mission is to advance and support the Five Keys to a future without FOP. RESEARCH, the key to a treatment and cure. EDUCATION, the key to preventing misdiagnosis and finding more FOP families. ADVOCACY, the key to living independently with full equality. HOPE, the key to support, survival and community. CURE, the key to a better future for those with FOP & the people who love them.

Heterotopic Bone Formation/Ossification (HO)

If you have a bad muscle strain or contusion (dead leg!) and it is neglected then you could be unlucky enough to get Myositis Ossificans. It is usually as a result of impact which causes damage to the sheath that surrounds a bone (periostium) as well as to the muscle. Bone will grow within the muscle (called calcification) which is painful. The bone will grow 2 to 4 weeks after the injury and be mature bone within 3 to 6 months.
Patient Information Uncertain