User:GhostRiver/fop

Presentation
A trademark symptom of fibrodysplasia ossificans progressiva (FOP) is a bilateral congenital malformation of the hallux valgus and great toe. While the exact nature of this malformation varies from a simple deviation of the toe's curvature to a complete absence of the digit, some malformation has been observed in more than 95% of observed FOP patients. Most commonly, the patient suffers from a shortened first metatarsal and proximal phalange, the appearance of which is often exaggerated by the altered angles at which those bones are set. With age, these shortened bones fuse together. While shortening of these bones manifests bilaterally, the degree of shortening is often asymmetrical. About half of patients also suffer from a congenital deformation of the thumbs.

Heterotopic ossification can begin anywhere from birth to 25 years of age, but the average age of onset is five. By seven years of age, most patients experience some restricted movement due to ossification, and by 15 years of age, many possess drastically limited arm mobility.

Causes
Fibrodysplasia ossificans progressiva is a genetic disorder caused by a spontaneous mutation of the activin A receptor, type I (ACVR1) gene. In every documented case of fibrodysplasia ossificans progressiva, whether familially or spontaneously manifesting, has involved a recurrent single nucleotide substitution on codon 206 of the ACVR1 gene, making it one of the most specific disease-causing mutations in the human genome.

Like many disorders caused by genetic mutations, increased paternal age shows a positive correlation with FOP diagnosis.

Because FOP is carried on an autosomal dominant allele, it is theoretically possible for the disease to pass from parent to child. In practice, however, the low reproductive fitness and shortened lifespan associated with the disease limits the number of cases that arise from genetic transmission. As of 2005, fewer than ten families have been identified as having inherited FOP, and the inheritance within those families has almost exclusively been limited to two generations. In one case where FOP was transmitted through three generations, both the proband and her father had been asymptomatic for the condition until adulthood, when they underwent surgery or experienced trauma.

Mechanism
Pathogenesis and pathophysiology

Diagnosis
Characteristic biopsy findings and differential diagnosis

The rarity of fibrodysplasia ossificans progressiva affects diagnostic patterns, as physicians may be unaware of the disease and subsequently misdiagnose their patients. One study estimated that approximately 87% of individuals with FOP were initially given an incorrect diagnosis, with one-third misdiagnosed with cancer. This misdiagnosis in turn led to unnecessary invasive surgical procedures or therapeutic treatments. The isolation of one recurrent genetic mutation in FOP has made it easier for doctors to ascertain the correct diagnosis through genetic testing of patients with the associated congenital toe malformation, even before heterotopic ossification begins.

Management
The rare nature of fibrodysplasia ossificans progressiva and the variability of phenotypic presentation make it difficult for researchers to conduct controlled studies on best management practices. Additionally, no naturally presenting animal models of FOP exist for researchers to conduct trials. As a result, most recommended treatments are derived from anecdotal data or imperfect clinical studies.

The 2006 discovery of the gene mutation responsible for the disease, however, has presented some potential treatment options, the focus of which is targeted inhibition of the activated ACVR1 receptor. A 2016 study found that palovarotene, a retinoic acid receptor gamma agonist, inhibited heterotopic ossification in mice while preserving joint, limb, and body motion, making it an attractive drug candidate to treat FOP. The drawbacks of palovarotene treatment are that it would require chronic administration, but that daily administration results in skeletal toxicity.


 * Activin A antibodies
 * Rapamycin
 * Imatinib

Prognosis
Fibrodysplasia ossificans progressiva results in a considerably shortened lifespan. The degree of this shortening, however, varies widely among patients. The most common cause of death in FOP patients is cardiorespiratory failure, often caused by thoracic insufficiency syndrome.

Epidemiology
The rare nature of FOP, as well as a potential lack of awareness within certain geographic communities, makes it difficult to ascertain how prevalent the disease is in the worldwide population. An early study indicated that FOP had a prevalence rate of 0.61 per one million individuals, but more recent analyses have estimated that the rate is closer to 0.88 per one million, or 1.36 per one million. While even these rates are believed to be lower than the actual worldwide prevalence due to undiagnosed cases, estimations of FOP's prevalence have become more accurate as care facilities for the disease have become centralized and registries have been created to list patients. The prevalence of FOP is consistent across gender, and it has been observed in equal rates across all racial and ethnic groups.

Within national populations, FOP tends to be more prevalent in more populous regions, where geographical clustering would be expected. Despite this, the prevalence of FOP varies dramatically across regions, ranging from 0.65 per million in North America, 0.47 per million in Western Europe, and 0.27 per million in Latin America to 0.05 per million in Africa and 0.04 per million in Asia and Oceania. It has been theorized that, like many rare diseases, FOP is underdiagnosed in geographic regions where there is less awareness of the disorder, as well as less regional and global infrastructure in place to connect patients to larger databases and registries. To assist with this latter issue, the International FOP Association created in 2018 the FOP Connection Registry, a voluntary database to capture disease and demographic information from both patients and physicians.

History
The first known description of fibrodysplasia ossificans progressiva arises from a letter that the French physician Guy Patin wrote to his colleague dated August 27, 1648, in which he describes a young woman who "turned to wood". A more detailed description of the disorder was published in 1740 by the English surgeon John Freke, who wrote to the Royal Society about a 14-year-old boy who was suffering from"many large swellings on his back which began about three years since", and which "make, as it were, a fixed bony pair of bodice".

Society and culture
Social perceptions, cultural history, stigma, economics, religious aspects, awareness, legal issues, notable cases

Two skeletons of patients with fibrodysplasia ossificans progressiva are on display at the Mütter Museum of the College of Physicians of Philadelphia. Harry Raymond Eastlack asked that his body be donated to science shortly before his death in 1973. The display of his skeleton allowed researchers at the Center for Research In FOP and Related Disorders in Philadelphia to examine the remains, and in 1995 and 2000, the museum lent Eastlack's skeleton to the International FOP Association for their annual symposium. In 2019, the skeleton of Carol Orzel joined Eastlack at the Mütter Museum. A Philadelphia native, Orzol was inspired to donate her body to science after seeing Eastlack's skeleton on display at the 1995 symposium.