Ghon focus

Ghon focus is a primary lesion usually subpleural, often in the mid to lower zones, caused by Mycobacterium tuberculosis. The focus is usually caseous and may eventually either become calcified or undergo fibrosis.

Definition

A Ghon focus is a small area of granulomatous inflammation that occurs in the lung tissue in response to infection with Mycobacterium tuberculosis. It is named after the Austrian pathologist Anton Ghon, who first described it in 1916. The Ghon focus represents the primary site of infection in the lungs and is an important component of primary tuberculosis.

Pathogenesis

The Ghon focus forms when Mycobacterium tuberculosis bacteria are inhaled into the lungs and are engulfed by alveolar macrophages. The bacteria multiply within the macrophages, which eventually die and release the bacteria into the surrounding tissue. This triggers an immune response, leading to the formation of a granuloma, or Ghon focus. The Ghon focus usually measures 1-1.5 cm in diameter and is located in the subpleural region of the lower or middle lobes of the lung.

Clinical Significance

The Ghon focus is usually asymptomatic and is often discovered incidentally on chest radiographs. It is a key component of primary tuberculosis, which is the initial infection with Mycobacterium tuberculosis. The presence of a Ghon focus, along with lymphadenopathy, is known as the Ghon complex, which is indicative of primary tuberculosis.

See Also

• Tuberculosis
• Mycobacterium tuberculosis
• Ghon complex
• Granuloma

References

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