Tuberculosis (pediatrics)

Tuberculosis (TB; TBC in Czech) is a chronic infectious disease caused by Mycobacterium tuberculosis. It affects mostly the lungs, extrapulmonary forms are less common and can affect any organ. Due to high vaccination rate of the Czech population the overall presence of TB is very low and extrapulmonary forms are rather exceptional. Higher rates of TB infection are notable among the elderly, the homeless, people addicted to alcohol or other addictive substances, the underprivileged and the immigrants. The diagnosis of TB is based on positive epidemiological anamnesis, chest X-ray, tuberculin test, bacteriological proof, biopsy and histological testing, and auxilliary examination methods. A combination of antibiotics is used as a treatment, which lasts at least 9 months. In the Czech republic, a vaccine is available, although it is not a part of the obligatory vaccination program.

A disease caused by related non-tuberculotic bacteria is called mycobacteriosis.

Etiology

 * Mycobacterium tuberculosis („Koch's bacillus“) is an acidoresistant rod-shaped bacteria;
 * small, immobile, slow growing bacillus;
 * very resistant against acidic environment;
 * when stained by the Ziehl-Neelsen method the rods are red against a blue background;
 * the M. tuberculosis complex includes:
 * M. bovis, M. africanum, M. microti, M. canetti;
 * M. bovis used to be a fairly common cause of infection before the advent of milk pasteurization;
 * non-tuberculotic mycobacteria:
 * Mycobacterium avium and M. kansasii – they cause severe illness which includes damage to lymphatic nodes as well as lung tissue (mycobacterioses);
 * M. leprae – the cause of leprosy.

Epidemiology

 * risk factors: weakened immunity, malnutrition, HIV positivity (at least ⅓ of people suffering from AIDS has an active tuberculosis), intravenous drug abuse, diabetes mellitus, chronic renal failure, cancer, lung silicosis, biological therapy by TNF-α inhibition;
 * transmission: droplet infection – contact with a diseased person that secretes M. tuberculosis into the sputum (active untreated TB);
 * the risk increases with the amount of bacteria and the frequency of exposition – the most dangerous are sources within families (a child is in frequent contact with the diseased person);
 * the source isn't usually discovered in extrapulmonary TB.

Pathogenesis

 * M. tuberculosis usually enters the organism through pulmonary alveoli → absorbed by the macrophages and antigen-presenting cells → contained in the regional lymph nodes (locus of primary infection + infected regional lymph node = primary complex) → if the infection isn't stopped, it progresses to postprimary form;
 * often the thoracic lymph nodes are infected primarily;
 * TB is a granulomatous inflammation with the participation of macrophages, T-lymphocytes, B-lymphocytes and fibroblasts → it creates a granuloma around the infectious agent, the granuloma is surrounded by lymphocytes → the granuloma prevents the infection from spreading and allows the cells of the immune system the elimination of bacteria controlled by interferon γ (activator of acrophages) → granulomas undergo a typical necrosis (caseous necrosis) → if any mycobacteria survive, it turns to a latent state with the risk of reactivation

The infection can be divided into primary and postprimary.


 * 1) Primary tuberculosis
 * 2) *happens after the first contact of the organism with the bacteria
 * 3) *its sign is the enlargement of lymph nodes (in both pulmonary and extrapulmonary forms)
 * 4) *it is the most common form of this disease in young age
 * 5) *a so-called primary complex appears – primary locus + lymphangoitis + lymphadenitis in the pulmonary hilum
 * 6) *during the creation of the primary complex the hematogenous spread is happening
 * 7) *it can remain latent or turn into postprimary forms
 * 8) *the primary pulmonary tuberculosis can be accompanied by – atelectasis (caused by the pressure of a swollen node against the bronchus – clean atelectasis; or by the prolapse of the node into the bronchus and the subsequent aspiration – unclean atelectasis)
 * 9) Postprimary tuberculosis
 * 10) *in persons who underwent primary tuberculosis
 * 11) *it is caused either by transition from primary form during unfortunate circumstances (puberty, weakened organism), or by endogenous reactivation of an older, untreated primary complex, rarely by exogenous superinfection
 * 12) *early forms – a few weeks or months after the first infection
 * 13) **hematogenous spread – acute miliary tuberculosis, tuberculotic meningitis, tuberculotic exsudative pleuritis
 * 14) *latent forms
 * 15) **after a period of one or more years after the first infection
 * 16) **bone and joint tuberculosis, urogenital tuberculosis, tuberculosis of the kidney