The disease has been reported to affect 3 per 1000 infants younger than 6 months in the United States. No predilection by race or sex has been established. Almost all cases occur by the age of 5 months. The familial form is inherited in an autosomal dominant fashion with variable penetrance. The familial form tends to have an earlier onset and is present at birth in 24% of cases, with an average age at onset of 6.8 weeks. The average age at onset for the sporadic form is 9–11 weeks.

Cortical hyperostosis is a potential side effect of long-term use of prostaglandins in neonates.

While the exact cause of enchondroma is not known, it is believed to occur either as an overgrowth of the cartilage that lines the ends of the bones, or as a persistent growth of original, embryonic cartilage.

An enchondroma may occur as an individual tumor or several tumors. The conditions that involve multiple lesions include the following:

- Ollier disease (enchondromatosis) - when multiple sites in the body develop the tumors. Ollier disease is very rare.

- Maffucci's syndrome - a combination of multiple tumors and angiomas (benign tumors made up of blood vessels).

Currently, the genetic or environmental factors that predispose an individual for chondroblastoma are not well known or understood. Chondroblastoma affects males more often than females at a ratio of 2:1 in most clinical reports. Furthermore, it is most often observed in young patients that are skeletally immature, with most cases diagnosed in the second decade of life. Approximately 92% of patients presenting with chondroblastoma are younger than 30 years. There is no indication of a racial predilection for chondroblastoma.

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.

Osteochondromas or osteocartilaginous exostoses are the most common benign tumors of the bones.

The tumors take the form of cartilage-capped bony projections or outgrowth on the surface of bones (exostoses). It is characterized as a type of overgrowth that can occur in any bone where cartilage forms bone. Tumors most commonly affect long bones in the leg, pelvis, or scapula (shoulder blade). Development of osteochondromas take place during skeletal growth between the ages of 13 and 15 and ceases when the growth plate fuses at puberty. They arise within the first three decades of life affecting children and adolescents.

Osteochondromas occur in 3% of the general population and represent 35% of all benign tumors and 8% of all bone tumors. Majority of these tumors are solitary non-hereditary lesions and approximately 15% of osteochondromas occur as hereditary multiple osteochondromas (HMOs). They can occur as a solitary lesion (solitary osteochondroma) or multiple lesions within the context of the same bone (Multiple Osteochondroma). Osteochondromas do not result from injury and the exact cause remains unknown. Recent research has indicated that multiple osteochondromas is an autosomal dominant inherited disease. Germ line Mutations in "EXT1" and "EXT2" genes located on chromosomes 8 and 11 have been associated with the cause of the disease.

The treatment choice for osteochondroma is surgical removal of solitary lesion or partial excision of the outgrowth, when symptoms cause motion limitations or nerve and blood vessel impingements.

Limited normal functions and movements are caused by osteochondromas growing slowly and inwardly. The majority of osteochondromas are symptomless and are found incidentally. Each individual with osteochondroma may experience symptoms differently and most of the time individuals will experience no symptoms at all. Some of the most common symptoms are a hard immobile painless palpable mass, adjacent muscle soreness, and pressure or irritation with heavy exercising.

Major symptoms arise when complications such as fractures, bone deformity or mechanical joint problems occur. If the occurrence of an osteochondroma is near a nerve or a blood vessel, the affected limb can experience numbness, weakness, loss of pulse or color change. Periodic changes in the blood flow can also take place. Approximately 20% of patients experiencing nerve compression commonly acknowledge vascular compression, arterial thrombosis, aneurysm, and pseudoaneurysm. Formation of pseudoaneurysm and venous thrombosis lead to claudication, pain, acute ischemia, and symptoms of phlebitis. If the tumor is found under a tendon, it can cause pain during movement causing restriction of joint motion. Pain can also occur due to bursal inflammation, swelling or fracture at the base of the tumor stalk. Some of the clinical signs and symptoms of malignant osteochondroma are pain, swelling, and mass enlargement.

The majority of cases occur in the second and third decades, with approximately 75% of cases occurring before the age of 30 years 1,12-15. There is no recognised gender predilection. Examples have however been seen in patients up to the age of 75 years. In some series there is a male predilection 12 whilst in others no such distribution is found 2

Although not specific to one mode of management, lesion size, patient sex, or follow-up, the recurrence rate for chondroblastoma is relatively high, and has been shown in select studies to be dependent upon the anatomical location, method of treatment, and biological aggressiveness of the initial lesion. The rate of recurrence is highly variable, ranging between 5% and 40%, as study results are generally inconclusive. However, local recurrence for long bone lesions is around 10%, with chondroblastoma in flat bones having higher recurrence and more complications. Recurrences are more common in cases involving an open epiphyseal plate where they can be attributed to inadequate curettage to avoid damage. Lesions of the proximal femur are particularly problematic because of difficulties accessing the femoral head for complete excision. Chondroblastoma may recur in the soft tissue surrounding the initial lesion, especially in the case of incomplete curettage. Recurrences have been shown to occur between 5 months and 7 years after initial treatment and are generally treated with repeat curettage and excision of affected soft-tissue. No histological differences have been seen between recurrent and non-recurrent chondroblastomas.

Rarely, more aggressive chondroblastomas can metastasize. The most common location for metastases is the lung, with some cases also involving secondary bone sites, soft tissue, skin, or the liver. The prevalence of metastatic chondroblastoma, however, is quite low and is believed to be less than 1%. There is no relationship established between metastasis and previous surgery, non-surgical treatment, anatomical location, or patient age. Survival of patients with metastatic lesions is better when the metastases are surgically resectable, as chemotherapy has been shown to have little to no benefit. Prognosis is bleak for patients with malignant chondroblastomas that are resistant to surgery, radiation, and chemotherapy. However, patients with resectable metastases have survived for several years following diagnosis.

While recurrence is the most common complication of chondroblastoma other issues include post-surgery infection, degenerative joint disease, pathological fractures, failure of bone grafts, pre-mature epiphyseal closure, functional impairment, and malignant transformation. Complications are less common in patients presenting with chondroblastoma in accessible areas. Overall, patients with more classical chondroblastoma (appearing in long bones, typical presentation) have better prognoses than patients with atypical chondroblastoma (flat bones, skull, etc.).

Fibrocartilaginous mesenchymoma of bone is (FCMB) is an extremely rare tumor first described in 1984. Fewer than 20 cases have been reported, with patient ages spanning from 9 to 25 years, though a case in a male infant aged 1 year and 7 months has been reported. Quick growth and bulky size are remarkable features of this tumor.

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.

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.

A nonossifying fibroma (also called fibroxanthoma) is a common benign bone tumor in children and adolescents. However, it is controversial whether it represents a true neoplasm or rather a developmental disorder of growing bone. Radiographically, the tumor presents as a well marginated radiolucent lesion, with a distinct multilocular appearance. These foci consist of collagen rich connective tissue, fibroblasts, histiocytes and osteoclasts. They originate from the growth plate, and are located in adjacent parts of the metaphysis and diaphysis of long bones, most often of the legs. No treatment is needed in asymptomatic patients and spontaneous remission with replacement by bone tissue is to be expected.

Multiple nonossifying fibromas occur in Jaffe-Campanacci syndrome in combination with cafe-au-lait spots, mental retardation, hypogonadism, ocular and cardiovascular abnormalities.

Chondromyxoid fibroma is a type of cartilaginous tumor.

Most cases are characterised by GRM1 gene fusion or promoter swapping. It can be associated with a translocation at t(1;5)(p13;p13).

A chondromyxoid fibroma (CMF) is an extremely rare benign cartilaginous neoplasm which accounts for < 1% bone tumours.

Surgery is curative despite possible local relapses. Wide resection of the tumor and resection arthrodesis with an intramedullary nail, vertebrectomy and femoral head allograft replacement of the vertebral body, resection of the iliac wing and hip joint disarticulation have been among the performed procedures.

The close resemblance of FCMB to fibrocartilaginous dysplasia has suggested to some scholars that they might be closely related entities, although the latter features woven bone trabeculae without osteoblastic rimming, which is a quite distinctive aspect. Instead the occurrence of epiphyseal plate-like cartilage is peculiar of the former.

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

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.

Malignant infantile osteopetrosis, also known as infantile autosomal recessive osteopetrosis or simply infantile osteopetrosis is a rare osteosclerosing type of skeletal dysplasia that typically presents in infancy and is characterized by a unique radiographic appearance of generalized hyperostosis - excessive growth of bone.

The generalized increase in bone density has a special predilection to involve the medullary portion with relative sparing of the cortices. Obliteration of bone marrow spaces and subsequent depression of the cellular function can result in serious hematologic complications. Optic atrophy and cranial nerve damage secondary to bony expansion can result in marked morbidity. The prognosis is extremely poor in untreated cases. Plain radiography provides the key information to the diagnosis. Clinical and radiologic correlations are also fundamental to the diagnostic process, with additional gene testing being confirmatory.

Osteochondrodysplasia or skeletal dysplasia is a general term for a disorder of the development (dysplasia) of bone ("osteo") and cartilage ("chondro").

Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia.

Infantile cortical hyperostosis is a self-limited condition, meaning that the disease resolves on its own without treatment, usually within 6–9 months. Long-term deformities of the involved bones, including bony fusions and limb-length inequalities, are possible but rare.

In the US, Osteoblastomas account for only 0.5-2% of all primary bone tumors and only 14% of benign bone tumors making it a relatively rare form of bone tumor.

In regards to morbidity and mortality, conventional osteoblastoma is a benign lesion with little associated morbidity. However, the tumor may be painful, and spinal lesions may be associated with scoliosis and neurologic manifestations. Metastases and even death have been reported with the controversial aggressive variant, which can behave in a fashion similar to that of osteosarcoma. This variant is also more likely to recur after surgery than is conventional osteoblastoma.

Osteoblastoma affects more males than it does females, with a ratio of 2-3:1 respectively. Osteoblastoma can occur in persons of any age, although the tumors predominantly affect the younger population (around 80% of these tumors occurs in persons under the age of 30). No racial predilection is recognized.

It usually presents in the vertebral column or long bones. Approximately 40% of all osteoblastomas are located in the spine. The tumors usually involve the posterior elements, and 17% of spinal osteoblastomas are found in the sacrum. The long tubular bones are another common site of involvement, with a lower extremity preponderance. Osteoblastoma of the long tubular bones is often diaphyseal, and fewer are located in the metaphysis. Epiphyseal involvement is extremely rare. Although other sites are rarely affected, several bones in the abdomen and extremities have been reported as sites of osteoblastoma tumors.

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.

An osteoid osteoma is a benign bone tumor that arises from osteoblasts and was originally thought to be a smaller version of an osteoblastoma. Osteoid osteomas tend to be less than 1.5 cm in size. The tumor can be in any bone in the body but are most common in long bones, such as the femur and tibia. They account for 10 to 12 percent of all benign bone tumors. "Osteoid osteomas may occur at any age, and are most common in patients between the ages of 4 and 25 years old. Males are affected approximately three times more commonly than females."

The cause of osteoblastoma is unknown. Histologically, osteoblastomas are similar to osteoid osteomas, producing both osteoid and primitive woven bone amidst fibrovascular connective tissue, the difference being that osteoblastoma can grow larger than 2.0 cm in diameter while osteoid osteomas cannot. Although the tumor is usually considered benign, a controversial aggressive variant has been described in the literature, with histologic features similar to those of malignant tumors such as an osteosarcoma.

In circumstances where other pathologies are excluded (for example, cancer), a pathologic fracture is diagnostic of osteoporosis irrespective of bone mineral density.