Achondrogenesis type 2

A rare genetic disorder affecting bone development

Achondrogenesis type 2 is a severe disorder of bone growth characterized by a short body, short limbs, and other skeletal abnormalities. It is a form of achondrogenesis, which is a group of disorders that affect cartilage and bone development. Achondrogenesis type 2 is specifically caused by mutations in the COL2A1 gene and is inherited in an autosomal dominant pattern.

Genetics

Achondrogenesis type 2 is caused by mutations in the COL2A1 gene, which provides instructions for making a component of type II collagen. Type II collagen is essential for the normal development of bones and other connective tissues. Mutations in the COL2A1 gene disrupt the production of type II collagen, leading to the severe skeletal abnormalities seen in this condition.

The disorder is inherited in an autosomal dominant manner, meaning that one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, the condition results from new mutations in the gene and occurs in people with no history of the disorder in their family.

Clinical Features

Individuals with achondrogenesis type 2 typically present with:

• Extremely short limbs (micromelia)
• A small chest with short ribs
• A prominent abdomen
• A flat face with a small chin
• Poor ossification of the spine and pelvis

These features are usually apparent at birth or can be detected prenatally through ultrasound. The condition is often lethal in the perinatal period due to respiratory failure caused by the underdeveloped thoracic cavity.

Diagnosis

Diagnosis of achondrogenesis type 2 is based on clinical examination, radiographic findings, and genetic testing. Prenatal diagnosis can be performed through ultrasound and confirmed with molecular genetic testing if a mutation in the COL2A1 gene is suspected.

Management

There is no cure for achondrogenesis type 2, and management is primarily supportive. Due to the severe nature of the condition, affected infants often do not survive beyond the neonatal period. Supportive care may include respiratory support and palliative care to ensure comfort.

Related pages

• Achondrogenesis
• Collagenopathy, types II and XI
• Skeletal dysplasia
• Autosomal dominant disorder

Gallery

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  Diagram showing autosomal dominant inheritance pattern