Table of ContentsView AllTable of ContentsTypesSymptomsCausesDiagnosisCan Osteopetrosis Be Treated?Prognosis
Table of ContentsView All
View All
Table of Contents
Types
Symptoms
Causes
Diagnosis
Can Osteopetrosis Be Treated?
Prognosis
Researchers have identified several different types of osteopetrosis, with varying degrees of severity. This article covers the types of osteopetrosis, along with its, symptoms, causes, and more.
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Types of Osteopetrosis
Osteopetrosis is classified based on symptoms, age of onset, and inheritance patterns. The most common types are autosomal dominant, autosomal recessive, intermediate autosomal osteopetrosis, and adult delayed-onset osteopetrosis.
Autosomal Dominant Osteopetrosis
Autosomal dominant osteopetrosis,Albers-Schönbergdisease, is the most common type of osteopetrosis, with an onset during adolescence or adulthood.
This type is associated with fractures of the long bones (bones that are longer than they are wide) or the posterior part of the vertebrae (bones of the spinal column). It may also lead toscoliosis,hip osteoarthritis,osteomyelitisof the mandible (bone infection of the lower jawbone),anemia(low red blood cells, RBCs), and/or septic osteitis (infection of the bone).
Autosomal Recessive Osteopetrosis (ARO)
Also called malignant infantile type, ARO develops early in infancy.It is known for fractures, impaired growth, thickening of the skull base leading to optic nerve compression, facial palsy, and hearing loss.
ARO is also associated with an absence of bone marrow cavity, leading to severe anemia,thrombocytopenia(a deficiency of platelets that leads to abnormal bleeding), recurrent infections, dental and tooth abnormalities, jaw infection and inflammation,hypocalcemia(low calcium levels), seizures, and too muchparathyroid hormone.
Without treatment, the maximum life span is around 10 years.
Intermediate Autosomal Osteopetrosis (IAO)
Adult Delayed-Onset Osteopetrosis
Adult delayed-onset osteopetrosis is a milder type of autosomal dominant osteopetrosis that begins during adulthood.
People with this type of osteopetrosis have normal bone structure at birth. Adult delayed-onset osteopetrosis is classified as benign. Up to 50% of people with adult-onset type are asymptomatic (without symptoms).
Bone mass will increase with age, but symptoms generally do not appear to affect health, brain function, or lifespan.A diagnosis of adult osteopetrosis is usually made based on bone abnormalities noted on imaging studies that are done for another purpose. Some people are diagnosed after developing osteomyelitis of the jaw.
Additional symptoms associated with adult-onset osteopetrosis include bone pain, fractures, back pain, and degenerative arthritis.
X-Linked Osteopetrosis
Osteopetrosis vs. OsteoporosisOsteopetrosis is essentially the opposite of osteoporosis. While osteopetrosis causes excess bone formation, osteoporosis causes bone mass to decrease.
Osteopetrosis vs. Osteoporosis
Osteopetrosis is essentially the opposite of osteoporosis. While osteopetrosis causes excess bone formation, osteoporosis causes bone mass to decrease.
Osteopetrosis Symptoms
Osteopetrosis causes excess bone formation and brittle bones. Mild types of osteopetrosis usually don’t cause symptoms or complications, but severe types can cause multiple signs and symptoms. These may include:
Autosomal dominant type osteopetrosis affects approximately 1 in 20,000 people, while autosomal recessive types affect approximately 1 in 250,000 people.Other types of osteopetrosis are rare and have been referenced in the medical literature.
Autosomal dominant inheritanceoccurs when only one copy of a mutated gene is necessary to cause the disorder.With this type of osteopetrosis, you inherit the condition from one affected parent.
Autosomal recessive inheritancemeans that two copies of a mutated gene are needed to cause the disorder.The parents of a person with the autosomal recessive disease will each carry at least one copy of the mutated gene. A parent of a person with a recessive disease can have the disease if they have two copies of the mutated gene—but parents with only one copy of the mutated gene wouldn’t show any signs of the condition.
X-linked recessive inheritancerefers to hereditary diseases linked to X chromosome mutations.These conditions tend to affect mostly genetic males because they carry only one X chromosome. In genetic females, who carry two X chromosomes—if they carry the gene mutation on only one X chromosome but not the other X chromosome, they would not show signs of a recessive X-linked disorder.
In about 30% of osteopetrosis cases, the cause of the condition is unknown.
Development
Osteoclasts are cells that are involved in the bone remodeling process, and they play a role in osteopetrosis.
Gene defects associated with osteopetrosis can lead to deficiency or dysfunction of osteoclasts. Without enough functioning osteoclasts, reabsorption is impaired, even as new bone tissue formation occurs. This is why bones become unusually dense and abnormally structured.
Osteopetrosis is usually suspected when X-rays or other imaging reveals bone abnormalities or increased bone density. Additional testing might be done to look for other problems, including those related to vision and hearing, blood composition, and brain abnormalities.
A bone biopsy can confirm a diagnosis, but this procedure is associated with a risk of infection.
Genetic testing can be done to confirm a diagnosis and determine the type of osteopetrosis. Genetic testing can also be helpful in determining prognosis, treatment response, and recurrence risks.
What Is Genetic Testing?
Treatment for infant and childhood types of osteopetrosis includes medications that affect bone formation and medications that treat various effects of the condition.
Calcitriol: This is a synthetic form ofvitamin D3that can be helpful in stimulating dormant osteoclasts to stimulate bone reabsorption.
Gamma interferon: Gamma interferon therapy is believed to increase WBC function and reduce infection risk. It can also help reduce bone mass volume and increase the size of the bone marrow. Combination therapy with calcitriol has been shown to improve long-term outcomes, but it is used with caution for treatment of infantile-type osteopetrosis.
Erythropoietin: A synthetic form of a hormone produced mainly in the kidneys can be used to increase the production of RBCs.
Corticosteroids:Corticosteroid therapy can help treat anemia and stimulate bone absorption.
Adult osteopetrosis does not usually require treatment, although complications of the disease need to be treated.
Procedures
The long-term outlook with osteopetrosis depends on the type and severity of the condition. Infantile types of osteopetrosis are associated with a shortened life expectancy, especially if untreated.
The prognosis of childhood and adolescent-onset osteopetrosis will depend on symptoms, including the fragility of bones and fracture risk.Life expectancy in adult-type osteoporosis is generally unaffected.
Summary
Osteopetrosis is a rare disorder. For many people, the condition causes mild or no symptoms. When it affects infants, children, and teens, parents should be aware of the possible complications of the disease and how to prevent such complications.
Treatments include bone marrow transplantation, ongoing medication, and surgery to repair fractures. Good nutrition is important for children and adults with osteopetrosis, including adequate calcium andvitamin D supplementation.
11 Sources
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