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31. Miliary tuberculosis of the lung: Difference between revisions
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Miliary tuberculosis a subtype of primary progressive tuberculosis characterized by the bacterium spreading to multiple organs that end up forming many very small (1-2 mm) granulomas. The bacterium in this case spreads by lymph or blood. The name comes from the x-ray morphology which looks like ''millet seeds'' spread throughout the lungs. | Miliary tuberculosis a subtype of primary progressive tuberculosis characterized by the bacterium spreading to multiple organs that end up forming many very small (1-2 mm) granulomas. The bacterium in this case spreads by lymph or blood. The name comes from the x-ray morphology which looks like ''millet seeds'' spread throughout the lungs. | ||
The granulomas are soft because they contain necrotic centres. Macroscopically we can see caseous necrosis. The granulomas are more numerous in the upper lobes. This is because the upper lobes are better ventilated (see pathophysiology), and the ''m. tuberculosis'' bacterium is highly aerobic.[[File:Miliary tuberculosis soft granuloma.jpg|thumb|A soft granuloma. The eosinophilic centre in the middle is necrotic semi-fluid.]] | The granulomas are soft because they contain necrotic centres. Macroscopically we can see caseous necrosis. The granulomas are more numerous in the upper lobes. This is because the upper lobes are better ventilated (see pathophysiology), and the ''m. tuberculosis'' bacterium is highly aerobic. The granulomatous inflammation in tuberculosis is due to a type 4 hypersensitivity reaction.[[File:Miliary tuberculosis soft granuloma.jpg|thumb|A soft granuloma. The eosinophilic centre in the middle is necrotic semi-fluid.]]The pigments that are present can be either: | ||
The pigments that are present can be either: | |||
* Haemosiderin in heart failure cells | * Haemosiderin in heart failure cells | ||