As of 2017, approximately 800 cases of FOP have been confirmed worldwide making FOP one of the rarest diseases known. The estimated incidence of FOP is 0.5 cases per million people and affects all races.

FOP is caused by an autosomal dominant allele on chromosome 2q23-24. The allele has variable expressivity, but complete penetrance. Most cases are caused by spontaneous mutation in the gametes; most people with FOP cannot or choose not to have children. A similar but less catastrophic disease is fibrous dysplasia, which is caused by a post-zygotic mutation.

A mutation in the gene ACVR1 (also known as activin-like kinase 2 (ALK2)) is responsible for the disease. ACVR1 encodes activin receptor type-1, a BMP type-1 receptor. The mutation causes substitution of codon 206 from arginine to histidine in the ACVR1 protein. This substitution causes abnormal activation of ACVR1, leading to the transformation of connective tissue and muscle tissue into a secondary skeleton. This causes endothelial cells to transform to mesenchymal stem cells and then to bone.

Opsismodysplasia is inherited in an autosomal recessive manner. This means the defective gene(s) responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Currently, no specific mutation in any gene has been found to cause the disorder.

It appears that the gene inositol polyphosphate phosphatase-like 1 is the cause of this condition in at least some cases.

Opsismodysplasia can be characterized by a delay in bone maturation, which refers to "bone aging", an expected sequence of developmental changes in the skeleton corresponding to the chronological age of a person. Factors such as gender and ethnicity also play a role in bone age assessment. The only indicator of physical development that can be applied from birth through mature adulthood is bone age. Specifically, the age and maturity of bone can be determined by its state of ossification, the age-related process whereby certain cartilaginous and soft tissue structures are transformed into bone. The condition of epiphyseal plates (growth plates) at the ends of the long bones (which includes those of the arms, hands, legs and feet) is another measurement of bone age. The evaluation of both ossification and the state of growth plates in children is often reached through radiography (X-rays) of the carpals (bones of the hand and wrist). In opsismodysplasia, the process of ossification in long bones can be disrupted by a failure of ossification centers (a center of organization in long bones, where cartilage cells designated to await and undergo ossification gather and align in rows) to form. This was observed in a 16-month-old boy with the disorder, who had no apparent ossification centers in the carpals (bones of the hand and wrist) or tarsals (bones of the foot). This was associated with an absence of ossification in these bones, as well as disfigurement of the hands and feet at age two. The boy also had no ossification occurring in the lower femur (thigh bone) and upper tibia (the shin bone).

Several studies have reported that life expectancy appears to be normal for people with CCD.

Osteofibrous dysplasia is treated with marginal resection with or without bone grafting, depending on the size of the lesion and the extent of bony involvement. However, due to the high rate of recurrence in skeletally immature individuals, this procedure is usually postponed until skeletal maturity.

Though the children affected with CLSD will have problems throughout life, the treatment for this disease thus far is symptomatic. However, prognosis is good; at the time of the most recently published articles, identified children were still alive at over 4 years of age.

Mutant proteins still maintain some residual activity, allowing for the release of some collagen, but still form an extremely distended endoplasmic reticulum.

Cranio–lenticulo–sutural dysplasia (CLSD, or Boyadjiev-Jabs syndrome) is a neonatal/infancy disease caused by a disorder in the 14th chromosome. It is an autosomal recessive disorder, meaning that both recessive genes must be inherited from each parent in order for the disease to manifest itself. The disease causes a significant dilation of the endoplasmic reticulum in fibroblasts of the host with CLSD. Due to the distension of the endoplasmic reticulum, export of proteins (such as collagen) from the cell is disrupted.

The production of SEC23A protein is involved in the pathway of exporting collagen (the COPII pathway), but a missense mutation causes and underproduction of SEC23A which inhibits the pathway, affecting collagen secretion. This decrease in collagen secretion can lead to the bone defects that are also characteristic of the disease, such as skeletal dysplasia and under-ossification. Decreased collagen in CLSD-affected individuals contributes to improper bone formation, because collagen is a major protein in the extracellular matrix and contributes to its proper mineralization in bones. It has also been hypothesized that there are other defects in the genetic code besides SEC23A that contribute to the disorder.

Myhre syndrome is a rare genetic disorder inherited in an autosomal dominant fashion. It is caused by mutation in SMAD4 gene.

It is usually autosomal dominant, but in some cases the cause is not known. It occurs due to haploinsufficiency caused by mutations in the CBFA1 gene (also called Runx2), located on the short arm of chromosome 6, which encodes transcription factor required for osteoblast differentiation. It results in delayed ossification of midline structures of the body, particularly membranous bone.

A new article reports that the CCD cause is thought to be due to a CBFA1 (core binding factor activity 1) gene defect on the short arm of chromosome 6p21 . CBFA1 is vital for differentiation of stem cells into osteoblasts, so any defect in this gene will cause defects in membranous and endochondral bone formation.

Osteofibrous dysplasia (also known as ossifying fibroma) is a rare, benign non-neoplastic condition with no known cause. It is considered a fibrovascular defect. Campanacci described this condition in two leg bones, the tibia and fibula, and coined the term. This condition should be differentiated from Nonossifying fibroma and fibrous dysplasia of bone.

Birt-Hogg-Dubé Syndrome patients, families, and caregivers are encouraged to join the NIH Rare Lung Diseases Consortium Contact Registry. This is a privacy protected site that provides up-to-date information for individuals interested in the latest scientific news, trials, and treatments related to rare lung diseases.

Winchester syndrome is believed to be inherited through autosomal recessive inheritance. For recessive genetic disorders, individuals inherit the mutated gene for the same trait from both parents. It believed that this disease is caused by a nonlysosomal connective-tissue disturbance. The protein inactivation mutation is found on the matrix metalloproteinase 2 gene (MMP2). MM2 is responsible for bone remodeling. Bone remodeling is the process in which old bone is destroyed so that new bone can be created to replace it. This mutation causes a multicentric osteolysis and arthritis syndrome. It is hypothesized that the loss of an upstream MMP-2 protein activator MT1-MMP, results in decreased MMP-2 activity without affecting "MMP2". The inactivating homoallelic mutation of "MT1-MMP" can be seen at the surface of fibroblasts. It was determined that fibroblasts lacking MT1-MMP lack the ability to degrade type I collagen which leads to anomalous function.

A review from 2000 stated that life expectancy was reduced because of a tendency to develop cancer relatively early as well as deaths due to infections related to immunodeficiency.

There is no known cure for Winchester syndrome; however, there are many therapies that can aid in the treatment of symptoms. Such treatments can include medications: anti-inflammatories, muscle relaxants, and antibiotics. Many individuals will require physical therapy to promote movement and use of the limbs affected by the syndrome. Genetic counseling is typically prescribed for families to help aid in the understanding of the disease. There are a few clinical trials available to participate in. The prognosis for patients diagnosed with Winchester syndrome is positive. It has been reported that several affected individuals have lived to middle age; however,the disease is progressive and mobility will become limited towards the end of life. Eventually, the contractures will remain even with medical intervention, such as surgery.

This disorder was first reported in 1981.

It has many similarities to LAPS Syndrome and they both arise from the same mutations in the SMAD4 gene. It is believed that they are the same syndrome.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

Johanson–Blizzard syndrome (JBS) is a rare, sometimes fatal autosomal recessive multisystem congenital disorder featuring abnormal development of the pancreas, nose and scalp, with mental retardation, hearing loss and growth failure. It is sometimes described as a form of ectodermal dysplasia.

The disorder is especially noted for causing profound developmental errors and exocrine dysfunction of the pancreas, and it is considered to be an inherited pancreatic disease.

A congenital disorder of glycosylation (previously called carbohydrate-deficient glycoprotein syndrome) is one of several rare inborn errors of metabolism in which glycosylation of a variety of tissue proteins and/or lipids is deficient or defective. Congenital disorders of glycosylation are sometimes known as CDG syndromes. They often cause serious, sometimes fatal, malfunction of several different organ systems (especially the nervous system, muscles, and intestines) in affected infants. The most common subtype is CDG-Ia (also referred to as PMM2-CDG) where the genetic defect leads to the loss of phosphomannomutase 2, the enzyme responsible for the conversion of mannose-6-phosphate into mannose-1-phosphate.

The disorder has been reported in more than 100 families worldwide, though some sources cite up to 400 families, and it is inherited in an autosomal dominant pattern. It is considered to be under-diagnosed because of the variability in its expression. The pattern of mutations and spectrum of symptoms are heterogeneous between individuals. Less severe skin phenotypes are seen in women and people of both sexes who have a late onset of skin symptoms.

The estimated incidence of Wiskott–Aldrich syndrome in the United States is one in 250,000 live male births. No geographical factor is present.

There is still some discussion on whether FND is sporadic or genetic. The majority of FND cases are sporadic. Yet, some studies describe families with multiple members with FND. Gene mutations are likely to play an important role in the cause. Unfortunately, the genetic cause for most types of FND remains undetermined.

Neurofibromatosis type I (NF-1) is a complex multi-system human disorder caused by the mutation of a gene on chromosome 17 that is responsible for production of a protein called neurofibromin which is needed for normal function in many human cell types. NF-1 causes tumors along the nervous system which can grow anywhere on the body. NF-1 is one of the most common genetic disorders and is not limited to any person's race or sex. NF-1 is an autosomal dominant disorder which means that mutation or deletion of one copy (or allele) of the NF-1 gene is sufficient for the development of NF-1 although presentation varies widely. Common symptoms of NF-1 include brownish-red spots in the colored part of the eye called Lisch nodules, benign skin tumors called neurofibromas, and larger benign tumors of nerves called plexiform neurofibromas, scoliosis (curvature of the spine), learning disabilities, vision disorders, mental disabilities, multiple café au lait (TCL, name of specifics spots) spots and epilepsy. NF-1 affected individuals also have a much higher rate of cancer and cardiovascular disease than the population in general.

NF-1 is a developmental syndrome caused by germline mutations in neurofibromin, a gene that is involved in the RAS pathway (RASopathy). Due to its rarity and to the fact that genetic diagnosis has been used only in recent years, in the past NF-1 was in some cases confused with another syndrome with vaguely similar symptoms, the Legius syndrome.

NF-1 is an age specific disease; most signs of NF-1 are visible after birth (during infancy), but many symptoms of NF-1 occur as the person ages and has hormonal changes. NF-1 was formerly known as von Recklinghausen disease after the researcher (Friedrich Daniel von Recklinghausen) who first documented the disorder.

The severity of NF-1 varies widely, and little is known about what causes a person to have a more severe or less severe case. Even within the same family (as there is a 50% chance that a parent will pass their condition to their offspring) levels of severity can vary enormously. However, 60% of people with NF-1 have mild cases, with few symptoms that have very little effect in their day-to-day lives. 20% of NF-1 patients have moderate cases, with several symptoms that have little more than cosmetic effects. The other 20% have severe cases with several symptoms that affect the person's quality of life. Even in this last group, symptoms are rarely life-threatening.

No treatment is available for most of these disorders. Mannose supplementation relieves the symptoms in PMI-CDG (CDG-Ib) for the most part, even though the hepatic fibrosis may persist. Fucose supplementation has had a partial effect on some SLC35C1-CDG (CDG-IIc or LAD-II) patients.

Trichothiodystrophy (TTD) is an autosomal recessive inherited disorder characterised by brittle hair and intellectual impairment. The word breaks down into "tricho" – "hair", "thio" – "sulphur", and "dystrophy" – "wasting away" or literally "bad nourishment". TTD is associated with a range of symptoms connected with organs of the ectoderm and neuroectoderm. TTD may be subclassified into four syndromes: Approximately half of all patients with trichothiodystrophy have photosensitivity, which divides the classification into syndromes with or without photosensitivity; BIDS and PBIDS, and IBIDS and PIBIDS. Modern covering usage is TTD-P (photosensitive), and TTD.