What are the other Names for this Condition? (Also known as/Synonyms)

• Autosomal Dominant Osteopetrosis Type 2
• OPTA2

What is Autosomal Dominant Osteopetrosis Type 2? (Definition/Background Information)

• Osteopetrosis refers to a group of rare, inherited skeletal disorders characterized by increased bone density and abnormal bone growth
• Symptoms and severity can vary greatly, ranging from neonatal onset with life-threatening complications (such as bone marrow failure) to the incidental finding of osteopetrosis on X-ray
• Depending on severity and age of onset, features may include fractures, short stature, compressive neuropathies (pressure on the nerves), hypocalcemia with attendant tetanic seizures, and life-threatening pancytopenia. In rare cases, there may be neurological impairment or involvement of other body systems
• Osteopetrosis may be caused by mutations in at least 10 genes. Inheritance can be autosomal recessive, autosomal dominant, or X-linked recessive with the most severe forms being autosomal recessive
• Management of Autosomal Dominant Osteopetrosis Type 2 depends on the specific symptoms and severity and may include vitamin D supplements, various medications, and/or surgery. Adult osteopetrosis requires no treatment by itself, but complications may require intervention

(Source: Autosomal Dominant Osteopetrosis Type 2; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Autosomal Dominant Osteopetrosis Type 2? (Age and Sex Distribution)

• Autosomal Dominant Osteopetrosis Type 2 is a rare congenital disorder. The presentation of symptoms may occur at birth
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Autosomal Dominant Osteopetrosis Type 2? (Predisposing Factors)

• A positive family history may be an important risk factor, since Autosomal Dominant Osteopetrosis Type 2 can be inherited
• Currently, no other risk factors have been clearly identified for the condition

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Autosomal Dominant Osteopetrosis Type 2? (Etiology)

• Autosomal Dominant Osteopetrosis Type 2 may be caused by mutations in at least 10 genes
• Inheritance can be autosomal recessive, autosomal dominant, or X-linked recessive with the most severe forms being autosomal recessive

(Source: Autosomal Dominant Osteopetrosis Type 2; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

What are the Signs and Symptoms of Autosomal Dominant Osteopetrosis Type 2?

The signs and symptoms of Autosomal Dominant Osteopetrosis Type 2 may include:

• Abnormality of pelvic girdle bone morphology
• Abnormality of the vertebral endplates
• Elevated serum acid phosphatase
• Facial paralysis
• Fractures of the long bones
• Hip osteoarthritis
• Osteopetrosis
• Visual loss

Very frequently present symptoms in 80-99% of the cases:

• Abnormality of epiphysis morphology
• Abnormality of the metacarpal bones
• Abnormality of the metaphysis
• Arthritis
• Aseptic necrosis
• Bone pain
• Facial palsy
• Frontal bossing
• Generalized osteosclerosis
• Joint dislocation
• Macrocephaly
• Mandibular osteomyelitis
• Osteoarthritis
• Recurrent fractures
• Short distal phalanx of finger

Frequently present symptoms in 30-79% of the cases:

• Anemia
• Genu valgum
• Optic atrophy

Occasionally present symptoms in 5-29% of the cases:

• Abnormality of leukocytes
• Blindness
• Bone marrow hypocellularity
• Carious teeth
• Hearing impairment
• Hydrocephalus
• Hypocalcemia

(Source: Autosomal Dominant Osteopetrosis Type 2; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Autosomal Dominant Osteopetrosis Type 2 Diagnosed?

Autosomal Dominant Osteopetrosis Type 2 is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Autosomal Dominant Osteopetrosis Type 2?

The complications of Autosomal Dominant Osteopetrosis Type 2 may include:

• Emotional stress
• Physical deformities
• Reduced quality of life

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Autosomal Dominant Osteopetrosis Type 2 Treated?

• Management of Autosomal Dominant Osteopetrosis Type 2 depends on the specific symptoms and severity and may include vitamin D supplements, various medications, and/or surgery
• Adult osteopetrosis requires no treatment by itself, but complications may require intervention

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

FDA-approved indication - Interferon gamma-1b: Delaying time to disease progression in patients with severe, malignant osteopetrosis.

(Source: Autosomal Dominant Osteopetrosis Type 2; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How can Autosomal Dominant Osteopetrosis Type 2 be Prevented?

Currently, Autosomal Dominant Osteopetrosis Type 2 may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Autosomal Dominant Osteopetrosis Type 2? (Outcomes/Resolutions)

• The prognosis of Autosomal Dominant Osteopetrosis Type 2 is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Autosomal Dominant Osteopetrosis Type 2:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/