肺結核 III - 分類

Tuberculosis is classified into six categories: Class zero indicates no TB exposure with negative tuberculin skin test. Class one shows TB exposure but no infection evidence. Class two represents latent TB infection with positive skin test but no clinical signs. Class three exhibits clinically active TB with positive skin test and disease evidence. Class four shows clinically non-active TB with prior episodes or stable radiographic findings. Class five indicates suspected TB with pending laboratory tests.

Latent TB infection occurs when Mycobacterium tuberculosis bacteria are dormant in the body without causing symptoms. Infected individuals feel healthy and cannot spread the infection. Clinically active TB, by contrast, displays positive tuberculin skin test results with clinical, bacteriological, or radiographic evidence of current disease, often accompanied by symptoms like persistent cough and fever.

Primary tuberculosis occurs when a person is infected with TB bacteria for the first time, and the immune system usually contains the bacteria without symptoms. Post-primary or secondary tuberculosis develops when a previously sensitized individual gets reinfected or when dormant bacteria become active. Post-primary TB is often symptomatic and can be more severe than primary infection.

Pulmonary tuberculosis, the most common TB type affecting the lungs, presents with persistent cough, chest pain, hemoptysis, fatigue, weight loss, reduced appetite, chills, fever, and night sweats. These symptoms result from bacterial infection of lung tissue and the body's inflammatory response to the infection.

Extrapulmonary tuberculosis occurs when Mycobacterium tuberculosis spreads from the initial infection site, usually the lungs, to other body parts via the bloodstream, lymphatic system, or direct extension. This can affect lymph nodes, spine, meninges, kidneys, bladder, reproductive organs, and digestive system, causing varied symptoms depending on affected organs.

Miliary tuberculosis is a disseminated TB form where Mycobacterium tuberculosis spreads widely through the bloodstream, forming small millet seed-sized lesions (1-5 mm) in multiple organs including lungs, liver, spleen, and bone marrow. The term derives from the lesions' resemblance to millet seeds visible on chest radiographs or during histological examination.

Extrapulmonary TB includes lymphatic TB affecting neck lymph nodes, skeletal TB causing spine and bone pain, TB meningitis affecting meninges with headaches and neurological issues, genitourinary TB affecting kidneys and bladder with flank pain, and gastrointestinal TB affecting digestive organs causing abdominal pain. Disseminated TB spreads to liver, spleen, kidneys, bones, and brain.