A Ghon focus is a primary lesion usually subpleural, often in the mid to lower zones, caused by ''

Mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...

bacilli Bacilli is a taxonomic class of bacteria that includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as ''Bacillus anthracis'' (the cause of anthrax). ''Bacilli'' are almost exclusively gram-posit ...

(

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in w ...

) developed in the lung of a nonimmune host (usually a child). It is named for Anton Ghon (1866–1936), an Austrian

pathologist Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...

. It is a small area of granulomatous inflammation, only detectable by

chest X-ray A chest radiograph, called a chest X-ray (CXR), or chest film, is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in med ...

if it calcifies or grows substantially (see tuberculosis radiology).Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; & Mitchell, Richard N. (2007). ''Robbins Basic Pathology'' (8th ed.). Saunders Elsevier. pp. 516-522 Typically these will heal, but in some cases, especially in immunosuppressed patients, it will progress to miliary tuberculosis (so named due to the

granulomas A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectiou ...

resembling

millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets also ...

seeds on a chest X-ray). The classical location for primary infection is surrounding the lobar fissures, either in the upper part of the lower lobe or lower part of the upper lobe. If the Ghon focus also involves infection of adjacent lymphatics and hilar lymph nodes, it is known as the

Ghon's complex Ghon's complex is a lesion seen in the lung that is caused by tuberculosis. The lesions consist of a Ghon focus along with pulmonary lymphadenopathy within a nearby pulmonary lymph node. A Ghons complex retains viable bacteria, making them sour ...

or primary complex. When a Ghon's complex undergoes fibrosis and calcification it is called a Ranke complex.

References

Tuberculosis Histopathology {{pathology-stub