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.

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.

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.

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.

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.

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.

The precise frequency of pycnodysostosis has not been determined. Pycnodysostosis can be classified in the large group of genetic diseases that are individually uncommon, but collectively important because of the sum of their numbers, and their heavy impact upon affected individuals.

This is an autosomal recessive osteochondrodysplasia that maps to chromosome 1q21. Deficiency of Cathepsin K, a cysteine protease in osteoclasts, is known to cause this condition. Cathepsin K became a much sought-after drug target in osteoporosis after the cause of pycnodysostosis was discovered. The disease consistently causes short stature. The height of adult males with the disease is less than . Adult females with the syndrome are even shorter.

The disease has been named Toulouse-Lautrec syndrome, after the French artist Henri de Toulouse-Lautrec, who may have had the disease. In 1996, the defective gene responsible for pycnodysostosis was located, offering accurate diagnosis, carrier testing and a more thorough understanding of this disorder.

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

Pathologic fractures in children and adolescents can result from a diverse array of disorders namely; metabolic, endocrine, neoplastic, infectious, immunologic, and genetic skeletal dysplasias.

- Osteogenesis imperfecta

- Primary hyperparathyroidism

- Simple bone cyst

- Aneurismal bone cyst

- Disuse osteoporosis

- Chronic osteomyelitis

- Osteogenesis imperfecta

- Rickets

- Renal osteodystrophy

- Malignant infantile osteopetrosis

- juvenile osteoporosis

- juvenile rheumatoid arthritis

Giant osteoclasts can occur in some diseases, including Paget's disease of bone and bisphosphonate toxicity.

An osteoclast (from the Greek words for "bone" (ὀστέον), and "broken" (κλαστός)) is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and remodelling of bones of the vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated protein and mineral at a molecular level by secreting acid and a collagenase, a process known as "bone resorption". This process also helps regulate the level of blood calcium.

An odontoclast (/odon·to·clast/; o-don´to-klast) is an osteoclast associated with absorption of the roots of deciduous teeth.

Infantile systemic hyalinosis or juvenile systemic hyalinosis is an allelic autosomal-recessive condition characterized by multiple skin nodules, hyaline deposition, gingival hypertrophy, osteolytic bone lesions, and joint contractures.

Galactosialidosis is a lysosomal storage disease.This condition is rare and most cases have been in the juvenile/adult group of patients. An infantile form has been described.

It is associated with cathepsin A.This disease is due to mutations in the CTSA gene which encodes the protective protein/cathepsin A (PPCA). This in turn leads to a secondary deficiency of beta-galactosidase (GLB1) and neuraminidase 1 (NEU1).There are three distinct CTSA isoforms.

Diffuse infantile fibromatosis is a condition affecting infants during the first 3 years of life. It is usually confined to the muscles of the arms, neck, and shoulder area. There is a multicentric infiltration of muscle fibers with fibroblasts resembling those seen in aponeurotic fibromas.

Chalkstick fractures are fractures, typically of long bones, in which the fracture is transverse to the long axis of the bone, like a broken stick of chalk. A healthy long bone typically breaks like a hard woody stick as the collagen in the matrix adds remarkable flexibility to the mineral and the energy can run up and down the growth rings of bone. The bones of children will even follow a greenstick fracture pattern.

Chalkstick fractures are particularly common in Paget's disease of bone, and osteopetrosis.

Infantile myofibromatosis (also known as "Congenital generalized fibromatosis," and "Congenital multicentric fibromatosis") is the most common fibrous tumor of infancy, in which eighty percent of patients have solitary lesions with half of these occurring on the head and neck, and 60% are present at or soon after birth. Less commonly, infantile myofibromatosis presents as multiple lesions of skin, muscle, and bone with about 1/3 of these cases also having lesions in their visceral organs. All of these cases have an excellent prognosis with their tumors sometimes regressing spontaneously except for those cases in which there is visceral involvement where the prognosis is poor. Infantile myofibromatosis and the classic form of mesoblastic nephroma have been suggested to be the same disease because of their very similar histology. However, studies on the distribution of cell-type markers (i.e. cyclin D1 and Beta-catenin) indicate that the two neoplasms likely have different cellular origins.

The GM1 gangliosidoses (or GM1 gangliosidos"i"s) are caused by a deficiency of beta-galactosidase, with resulting abnormal storage of acidic lipid materials in cells of the central and peripheral nervous systems, but particularly in the nerve cells.

GM1 Gangliosidoses are inherited, autosomal recessive sphingolipidoses, resulting from marked deficiency of Acid Beta Galactosidase.

Pipecolic acidemia, also called hyperpipecolic acidemia or hyperpipecolatemia, is a very rare autosomal recessive metabolic disorder that is caused by a peroxisomal defect.

Pipecolic acidemia can also be an associated component of Refsum disease with increased pipecolic acidemia (RDPA), as well as other peroxisomal disorders, including both infantile and adult Refsum disease, and Zellweger syndrome.

The disorder is characterized by an increase in pipecolic acid levels in the blood, leading to neuropathy and hepatomegaly.

Acropustulosis refers to Acrodermatitis with pustular involvement.

Types include:

- Pustulosis palmaris et plantaris

- Infantile acropustulosis

Infants with Schindler disease tend to die within 4 years of birth, therefore, treatment for this form of the disease is mostly palliative. However, Type II Schindler disease, with its late onset of symptoms, is not characterized by neurological degeneration. There is no known cure for Schindler disease, but bone marrow transplants have been trialed, as they have been successful in curing other glycoprotein disorders.

The term fibromatosis refers to a group of soft tissue tumors which have certain characteristics in common, including absence of cytologic and clinical malignant features, a histology consistent with proliferation of well-differentiated fibroblasts, an infiltrative growth pattern, and aggressive clinical behavior with frequent local recurrence. It is classed by the World Health Organisation as an intermediate soft tissue tumor related to the sarcoma family.

Infantile digital fibromatosis (also known as an "Inclusion body fibromatosis," "Infantile digital myofibroblastoma," and "Reye tumor") usually occurs as a small, asymptomatic, nodular, dermal fibrous proliferation at the extensor or lateral surface of a finger or toe.

Subtypes of fibromatosis include -

- Juvenile fibromatosis

- Fibromatosis colli: Non-neoplastic sternocleidomastoid muscle enlargement in early infancy. Does not generally require resection and responds well to physiotherapy.

- Infantile digital fibromatosis

- Infantile myofibromatosis

- Ipofibromatosis

- Fibromatosis hyalinica multiplex

- Plantar fibromatosis

- Penile fibromatosis (Peyronie's disease)

- Palmar fibromatosis (Dupuytren's contracture)