Ghon focus

An initial lesion in primary pulmonary tuberculosis

Ghon focus

Chest X-ray showing a Ghon focus

A Ghon focus is a primary lesion in the lung that is associated with primary tuberculosis. It is named after the Austrian pathologist Anton Ghon, who first described it. The Ghon focus is typically a small area of granulomatous inflammation, usually located in the subpleural region of the lung, often in the upper part of the lower lobe or the lower part of the upper lobe.

Pathophysiology

The formation of a Ghon focus occurs when Mycobacterium tuberculosis bacilli are inhaled and reach the alveoli of the lungs. The body's immune response leads to the formation of a granuloma, which is a collection of macrophages, lymphocytes, and other immune cells that attempt to contain the infection. The center of the granuloma may undergo caseous necrosis, a form of cell death that gives the lesion a cheese-like appearance.

Ghon complex

A Ghon focus, when associated with lymphatic spread to the regional lymph nodes, forms a Ghon complex. This complex is a hallmark of primary tuberculosis infection. The lymph nodes involved are typically the hilar or mediastinal nodes. Over time, the Ghon complex may calcify, becoming visible on a chest X-ray as a calcified nodule.

Clinical significance

In most cases, a Ghon focus is asymptomatic and may heal spontaneously, especially in individuals with a competent immune system. However, in some cases, the infection can progress to active tuberculosis, particularly if the immune system is compromised. The presence of a Ghon focus is an indication of prior exposure to tuberculosis and can be an important finding in the diagnosis of the disease.

Diagnosis

A Ghon focus is often identified through imaging studies, such as a chest X-ray or CT scan. On a chest X-ray, it may appear as a small, round opacity, often with associated calcification if the lesion has healed. In some cases, a tuberculin skin test or an interferon-gamma release assay may be used to support the diagnosis of tuberculosis infection.

Treatment

The presence of a Ghon focus itself does not require treatment unless there is evidence of active tuberculosis. In cases of active disease, a combination of antitubercular drugs is used to treat the infection. These drugs typically include isoniazid, rifampicin, ethambutol, and pyrazinamide.

Related pages

• Tuberculosis
• Mycobacterium tuberculosis
• Granuloma
• Caseous necrosis
• Lymph node