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Approximately eight to 40 children are born in the United States each year with the malignant infantile type of osteopetrosis. One in every 100,000 to 500,000 individuals is born with this form of osteopetrosis. Higher rates have been found in Denmark and Costa Rica. Males and females are affected in equal numbers.

The adult type of osteopetrosis affects about 1,250 individuals in the United States. One in every 200,000 individuals is affected by the adult type of osteopetrosis. Higher rates have been found in Brazil. Males and females are affected in equal numbers.

The odds are greater in the Russian region of Mari El (1 of every 14,000 newborns) and much greater in Chuvashia (1 of every 3,500—4,000 newborns) due to genetic features of the Mari people and Chuvash people, respectively.

Osteogenesis imperfecta is a rare condition in which bones break easily. There are multiple genetic mutations in different genes for collagen that may result in this condition. It can be treated with some drugs to promote bone growth, by surgically implanting metal rods in long bones to strengthen them, and through physical therapy and medical devices to improve mobility.

Fibrous dysplasia is a disorder where normal bone and marrow is replaced with fibrous tissue, resulting in formation of bone that is weak and prone to expansion. As a result, most complications result from fracture, deformity, functional impairment, and pain. Disease occurs along a broad clinical spectrum ranging from asymptomatic, incidental lesions to severe disabling disease. Disease can affect one bone (monostotic) or multiple (polyostotic), and may occur in isolation or in combination with cafe-au-lait skin macules and hyperfunctioning endocrinopathies, termed McCune-Albright syndrome. More rarely, fibrous dysplasia may be associated with intramuscular myxomas, termed Mazabraud's syndrome. Fibrous dysplasia is very rare, and there is no known cure. Fibrous dysplasia is not a form of cancer.

"Achondroplasia" is a type of autosomal dominant genetic disorder that is the most common cause of dwarfism. Achondroplastic dwarfs have short stature, with an average adult height of 131 cm (4 feet, 3 inches) for males and 123 cm (4 feet, 0 inches) for females.

The prevalence is approximately 1 in 25,000 births.

Men and women are affected in equal number., reflecting the fact that osteopoikilosis attacks indiscriminately. Additionally, the disease is often associated with melorheostosis, despite the apparent lack of correlation between melorheostosis and genetic heritability. It has been tied to LEMD3. Buschke-Ollendorff syndrome is a similar condition, which is also associated with LEMD3.

Polyostotic fibrous dysplasia is a form of fibrous dysplasia affecting more than one bone.

McCune-Albright syndrome includes polyostotic fibrous dysplasia as part of its presentation.

One treatment that has been used is bisphosphonates.

Pseudoachondroplasia is inherited in an autosomal dominant manner, though one case of a very rare autosomal recessive form has been documented. The offspring of affected individuals are at 50% risk of inheriting the mutant allele. Prenatal testing by molecular genetic examination is available if the disease-causing mutation has been identified in an affected family member (Hecht et al. 1995).

The only effective line of treatment for malignant infantile osteopetrosis is hematopoietic stem cell transplantation. It has been shown to provide long-term disease-free periods for a significant percentage of those treated; can impact both hematologic and skeletal abnormalities; and has been used successfully to reverse the associated skeletal abnormalities.

Radiographs of at least one case with malignant infantile osteopetrosis have demonstrated bone remodeling and recanalization of medullar canals following hematopoietic stem cell transplantation. This favorable radiographic response could be expected within one year following the procedure - nevertheless, primary graft failure can prove fatal.

Treatment in fibrous dysplasia is mainly palliative, and is focused on managing fractures and preventing deformity. There are no medications capable of altering the disease course. Intravenous bisphosphonates may be helpful for treatment of bone pain, but there is no clear evidence that they strengthen bone lesions or prevent fractures. Surgical techniques that are effective in other disorders, such as bone grafting, curettage, and plates and screws, are frequently ineffective in fibrous dysplasia and should be avoided. Intramedullary rods are generally preferred for management of fractures and deformity in the lower extremities. Progressive scoliosis can generally be managed with standard instrumentation and fusion techniques. Surgical management in the craniofacial skeleton is complicated by frequent post-operative FD regrowth, and should focus on correction of functional deformities. Prophylactic optic nerve decompression increases the risk of vision loss and is contraindicated.

Managing endocrinopathies is a critical component of management in FD. All patients with fibrous dysplasia should be evaluated and treated for endocrine diseases associated with McCune–Albright syndrome. In particular untreated growth hormone excess may worsen craniofacial fibrous dysplasia and increase the risk of blindness. Untreated hypophosphatemia increases bone pain and risk of fractures.

Pseudoachondroplasia is one of the most common skeletal dysplasias affecting all racial groups. However, no precise incidence figures are currently available (Suri et al. 2004).

Spondyloepimetaphyseal dysplasia is a genetic condition affecting the bones.

Types include:

- Spondyloepimetaphyseal dysplasia, Strudwick type

- Spondyloepiphyseal dysplasia congenita

- Spondyloepimetaphyseal dysplasia, Pakistani type

Multiple epiphyseal dysplasia (MED) encompasses a spectrum of skeletal disorders, most of which are inherited in an autosomal dominant form. However, there is an autosomal recessive form.

Associated genes include COL9A1, COL9A2, COL9A3, COMP, and MATN3.

Types include:

Fibrochondrogenesis is quite rare. A 1996 study from Spain determined a national minimal prevalence for the disorder at 8 cases out of 1,158,067 live births.

A United Arab Emirates (UAE) University report, from early 2003, evaluated the results of a 5-year study on the occurrence of a broad range of osteochondrodysplasias. Out of 38,048 newborns in Al Ain, over the course of the study period, fibrochondrogenesis was found to be the most common of the recessive forms of osteochondrodysplasia, with a prevalence ratio of 1.05:10,000 births.

While these results represented the most common occurrence within the group studied, they do not dispute the rarity of fibrochondrogenesis. The study also included the high rate of consanguinous marriages as a prevailing factor for these disorders, as well as the extremely low rate of diagnosis-related pregnancy terminations throughout the region.

The frequency of this disorder is unknown, but it is very rare. Only a few families with the condition have been reported.

Monostotic fibrous dysplasia (or monostotic osteitis fibrosa) is a form of fibrous dysplasia where only one bone is involved. It comprises a majority of the cases of fibrous dysplasia.

A rare bone disorder characterized by benign bone growths which can cause very painful swellings and bone deformities and makes bone prone to fractures.

The differential diagnosis of malignant infantile osteopetrosis includes other genetic skeletal dysplasias that cause osteosclerosis. They are collectively known as osteosclerosing dysplasias. The differential diagnosis of genetic osteosclerosing dysplasias including infantile osteopetrosis has been tabulated and illustrated in literature citations.

- Neuropathic infantile osteopetrosis

- Infantile osteopetrosis with renal tubular acidosis

- Infantile osteopetrosis with immunodeficiency

- IO with leukocyte adhesion deficiency syndrome (LAD-III)

- Intermediate osteopetrosis

- Autosomal dominant osteopetrosis (Albers-Schonberg)

- Pyknodysostosis (osteopetrosis acro-osteolytica)

- Osteopoikilosis (Buschke–Ollendorff syndrome)

- Osteopathia striata with cranial sclerosis

- Mixed sclerosing bone dysplasia

- Progressive diaphyseal dysplasia (Camurati–Engelmann disease)

- SOST-related sclerosing bone dysplasias

The disorder is progressive, with the ultimate severity of symptoms often depending on age of onset. In severe cases amputation has been performed when conservative measures such as physical therapy and regional anesthetics have been ineffective.

Spondyloperipheral dysplasia is one of a spectrum of skeletal disorders caused by mutations in the "COL2A1" gene, located on chromosome 12q13.11-q13.2. The protein made by this gene forms type II collagen, a molecule found mostly in cartilage and in the clear gel that fills the vitreous humour (the eyeball). Type II collagen is essential for the normal development of bones and other connective tissues (the tissues that form the body's supportive framework).

Mutations in the "COL2A1" gene interfere with the assembly of type II collagen molecules. The protein made by the altered "COL2A1" gene cannot be used to make type II collagen, resulting in a reduced amount of this type of collagen in the body. Instead of forming collagen molecules, the abnormal protein builds up in cartilage cells (chondrocytes). These changes disrupt the normal development of bones, leading to the signs and symptoms of spondyloperipheral dysplasia.

The disorder is believed to be inherited in an autosomal dominant manner. This indicates that the defective gene responsible for the disorder is located on an autosome (chromosome 12 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

Platyspondylic lethal skeletal dysplasia, Torrance type is a severe disorder of bone growth. People with this condition have very short arms and legs, a small chest with short ribs, underdeveloped pelvic bones, and unusually short fingers and toes (brachydactyly). This disorder is also characterized by flattened spinal bones (platyspondyly) and abnormal curvature of the spine (lordosis).

As a result of these serious skeletal problems, many infants with platyspondylic lethal skeletal dysplasia, Torrance type are born prematurely, are stillborn, or die shortly after birth from respiratory failure. A few affected people with milder signs and symptoms have lived into adulthood, however.

This condition is one of a spectrum of skeletal disorders caused by mutations in the "COL2A1" gene. This gene provides instructions for making a protein that forms type II collagen. This type of collagen is found mostly in cartilage and in the clear gel that fills the eyeball (the vitreous). It is essential for the normal development of bones and other tissues that form the body's supportive framework (connective tissues).

Mutations in the "COL2A1" gene interfere with the assembly of type II collagen molecules, resulting in a reduced amount of this type of collagen in the body. Instead of forming collagen molecules, the abnormal "COL2A1" protein builds up in cartilage cells (chondrocytes). These changes disrupt the normal development of bones and other connective tissues, leading to the skeletal abnormalities characteristic of platyspondylic lethal skeletal dysplasia, Torrance type.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In some cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.

Some studies suggest a hormonal link. Specifically, the hormone relaxin has been indicated.

A genetic factor is indicated since the trait runs in families and there is an increased occurrence in some ethnic populations (e.g., Native Americans, Lapps / Sami people). A locus has been described on chromosome 13. Beukes familial dysplasia, on the other hand, was found to map to an 11-cM region on chromosome 4q35, with nonpenetrant carriers not affected.

Fairbank's disease or multiple epiphyseal dysplasia (MED) is a rare genetic disorder (dominant form: 1 in 10,000 births) that affects the growing ends of bones. Long bones normally elongate by expansion of cartilage in the growth plate (epiphyseal plate) near their ends. As it expands outward from the growth plate, the cartilage mineralizes and hardens to become bone (ossification). In MED, this process is defective.

Spondyloperipheral dysplasia is an autosomal dominant disorder of bone growth. The condition is characterized by flattened bones of the spine (platyspondyly) and unusually short fingers and toes (brachydactyly). Some affected individuals also have other skeletal abnormalities, short stature, nearsightedness (myopia), hearing loss, and mental retardation. Spondyloperipheral dysplasia is a subtype of collagenopathy, types II and XI.

A recent article in 2015 reported a persistent notochord in a fetus at 23 weeks of gestation. The fetus had an abnormal spine, shortened long bones and a left clubfoot. After running postmortem tests and ultrasound, the researchers believed that the fetus suffered from hypochondrogenesis. Hypochondrogenesis is caused when type II collagen is abnormally formed due to a mutation in the COL2A1 gene. Normally, the cartilaginous notochord develops into the bony vertebrae in a human body. The COL2A1 gene results in malformed type II collagen, which is essential in the transition from collagen to bone. This is the first time that researchers found a persistent notochord in a human body due to a COL2A1 mutation.

Melorheostosis is a medical developmental disorder and mesenchymal dysplasia in which the bony cortex widens and becomes hyperdense in a sclerotomal distribution. The condition begins in childhood and is characterized by thickening of the bones. Pain is a frequent symptom and the bone can have the appearance of dripping candle wax.