Familial osteochondritis dissecans

Familial osteochondritis dissecans

Alternate names - Osteochondritis dissecans, short stature, and early-onset osteoarthritis

Definition

Osteochondritis dissecans is a joint condition that occurs when a piece of cartilage and the thin layer of bone beneath it, separates from the end of the bone.

Cartilage is a tough but flexible tissue that covers the ends of the bones at joints and is also part of the developing skeleton.

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Summary

• If the piece of cartilage and bone remain close to where they detached, they may not cause any symptoms. However, affected people may experience pain, weakness and/or decreased range of motion in the affected joint if the cartilage and bone travel into the joint space.
• A similar condition called sporadic osteochondritis dissecans is associated with a single lesion in one joint, most often the knee.
• These cases may be caused by injury to or repetitive use of the joint (often sports-related).
• Some people with sporadic osteochondritis dissecans develop osteoarthritis in the affected joint, especially if the lesion occurs later in life after the bone has stopped growing.
• Short stature is not associated with this form of the condition.

Epidemiology

Familial osteochondritis dissecans is a rare condition, although the prevalence is unknown. Sporadic osteochondritis dissecans is more common; it is estimated to occur in the knee in 15 to 29 per 100,000 individuals.

Cause

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• Mutation of the ACAN gene can cause familial osteochondritis dissecans.
• The ACAN gene provides instructions for making the aggrecan protein, which is a component of cartilage.
• Aggrecan attaches to the other components of cartilage, organizing the network of molecules that gives cartilage its strength.
• In addition, aggrecan attracts water molecules and gives cartilage its gel-like structure.
• This feature enables the cartilage to resist compression, protecting bones and joints.

Gene mutations

• The ACAN gene mutation associated with familial osteochondritis dissecans results in an abnormal protein that is unable to attach to the other components of cartilage.
• As a result, the cartilage is disorganized and weak.
• It is unclear how the abnormal cartilage leads to the lesions and osteoarthritis characteristic of familial osteochondritis dissecans.
• Researchers suggest that a disorganized cartilage network in growing bones impairs their normal growth, leading to short stature.
• Sporadic osteochondritis dissecans is not caused by genetic changes and is not inherited.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

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.

Signs and symptoms

• The signs and symptoms of osteochondritis dissecans vary from person to person.
• If the piece of cartilage and bone remain close to where they detached, they may not cause any symptoms.

However, affected people may experience the following if the cartilage and bone travel into the joint space:

• Pain, swelling and/or tenderness
• Joint popping
• Joint weakness
• Decreased range of motion

Although osteochondritis dissecans can develop in any joint of the body, the knee, ankle and elbow are most commonly affected. Most people only develop the condition in a single joint.

Diagnosis

• A diagnosis of osteochondritis dissecans is usually suspected based on the presence of characteristic signs and symptoms.
• Additional testing can then be ordered to confirm the diagnosis.
• These test may include x-rays, magnetic resonance imaging (MRI) and/or computed tomography (CT scan).

Treatment

• The primary aim of treatment for osteochondritis dissecans is to restore normal function of the affected joint, relieve pain and prevent osteoarthritis.
• Treatment for the condition varies depending on many factors including the age of the affected person and the severity of the symptoms.
• In children and young teens, osteochondritis dissecans often heals overtime without surgical treatment.
• These cases are often managed with rest and in some cases, crutches and/or splinting to relieve pain and swelling.
• If non-surgical treatments are not successful or the case is particularly severe (i.e. the cartilage and bone are moving around within the joint space), surgery may be recommended.
• Following surgery, physical therapy is often necessary to improve the strength and range of motion of the affected joint.

NIH genetic and rare disease info

• NIH info on Familial osteochondritis dissecans

Familial osteochondritis dissecans is a rare disease.

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