Metachondromatosis

Metachondromatosis
Synonyms	METCDS
Pronounce
Field	Orthopedics, Medical genetics
Symptoms	Multiple enchondromas, osteochondromas, bone pain, cranial nerve paralysis
Complications	Avascular necrosis, deformity, nerve damage
Onset	Typically in the first decade of life
Duration	Lifelong, with variable progression
Types
Causes	PTPN11 gene mutations
Risks	Genetic predisposition, family history
Diagnosis	Clinical evaluation, radiographic findings, genetic testing
Differential diagnosis	Hereditary multiple osteochondromas (HMO)
Prevention	Genetic counseling for at-risk families
Treatment	Symptomatic management, surgical removal of lesions if necessary
Medication	Pain management
Prognosis	Generally good with appropriate treatment; may have cosmetic deformities
Frequency	Rare, with limited documented cases
Deaths	Uncommon, unless complicated by severe bone deformities or associated conditions

Alternate names

• METCDS

Definition

Metachondromatosis (MC) is a rare genetic bone disorder characterized by the presence of both multiple enchondromas and osteochondroma-like lesions. The condition typically presents in childhood and can cause bone deformities and growth abnormalities.

Cause

The condition has been linked to mutations in the PTPN11 gene in several families, which plays a role in the signaling pathways that regulate cell growth and differentiation.

Inheritance

Metachondromatosis is inherited in an autosomal dominant manner, meaning an affected person has a 50% chance of passing the condition on to their offspring.

Onset

The first signs of metachondromatosis usually appear during the first decade of life, often before the age of 10.

Signs and symptoms

The symptoms of metachondromatosis are primarily due to the presence of multiple enchondromas and osteochondromas. Common symptoms include:

• Enchondromas: Benign tumors that form inside the bones, often in the iliac crests, femur, and other long bones. These tumors are typically painless but can cause deformity when located in the hands and feet.
• Osteochondromas: Tumors that form on the surface of bones, typically near the growth plates. Most commonly found in the small bones of the hands and feet, these may cause bumps or discomfort if they press against soft tissues, nerves, or blood vessels.
• Bone pain, particularly in the affected areas, such as the pelvis and long bones.
• Deformities in the hands and feet due to the growth of multiple tumors.
• Exostoses: New, benign bone growth on existing bone, which may lead to deformities.
• Avascular necrosis: Death of bone tissue due to a lack of blood supply, which can cause pain and mobility issues.
• Cranial nerve paralysis: Rare but may occur in severe cases.

Clinical presentation

The clinical presentation varies, but typically includes the following:

80%-99% of people with MC exhibit:

• Abnormal epiphyseal morphology (altered shape of the end part of the bone)
• Abnormalities in the metaphysis (wide portion of long bones)
• Avascular necrosis
• Bone pain or tenderness
• Exostoses (benign bone growth)
• Multiple enchondromas

Diagnosis

The diagnosis of metachondromatosis is based on clinical evaluation, radiographic findings, and genetic testing. Characteristic radiological features include the presence of multiple enchondromas and osteochondromas in specific areas of the body, such as the iliac crests, femur, and hands or feet.

Genetic testing for mutations in the PTPN11 gene can confirm the diagnosis. A recent case report also described a family with radiographic features of both metachondromatosis and hereditary multiple osteochondromas (HMO), and a mutation of the EXT-2 gene, highlighting a potential overlap of these two disorders.

Treatment

Treatment is symptomatic and focused on managing pain and addressing deformities. Surgical removal of troublesome osteochondromas may be necessary if they cause pain or functional impairment. In some cases, physical therapy may help improve mobility and manage any musculoskeletal issues that arise due to the presence of bone tumors.

Regular monitoring through radiographs is important to assess the progression of the condition and detect any new growths or changes in existing lesions. Pain management may include the use of nonsteroidal anti-inflammatory drugs (NSAIDs) or other analgesics.

Prognosis

The prognosis for individuals with metachondromatosis is generally good with appropriate treatment, particularly for those without severe complications. However, cosmetic deformities and limited range of motion due to bone growths may occur. In severe cases, untreated bone deformities or complications such as avascular necrosis can lead to disability.

See Also

• Hereditary multiple osteochondromas (HMO)
• Enchondroma
• Osteochondroma
• Exostosis