Early stages of tuberculosis

Primary tuberculosis is known as an infection in an individual who has not been infected previously.

Description

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis, which primarily typically affects the lungs (so-called pulmonary TB) but may also involve other organs (extrapulmonary TB), especially in immunocompromised individuals (those who have inborn or acquired immunodeficiency, for example due to HIV).

Primary tuberculosis

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The bacilli-containing nuclei reach the terminal parts of the lungs where bacteria are being kept under control/or killed by the person’s defense system and the infection may remain dormant for decades or even lifelong. In about 5% of healthy individuals within 18 months after he/she was infected.  People with compromised immune system are even at greater risk of developing tuberculosis soon after acquiring the infection.

The primary complex 

Primary tuberculosis typically affects the middle and lower lung lobes because the inspired air that carries the bacteria is typically distributed to these areas. Usually the lesion known as the Ghon focus is seen peripherally whilst the hilar and paratracheal lymph nodes also appear enlarged due to the dissemination of the bacteria via lymphatic vessels to the nearest lymph nodes, forming the primary complex. In the center of the Ghon focus approximately within 4-8 weeks forms the area of caseation (the immune system kills bacteria by causing inflammation and the formation of granuloma).  The lesion tends to heal spontaneously leaving a small calcified nodule (the Ranke complex) in individuals with the adequate immune response. Enlarged lymph nodes may compress the airways and cause the collapse of the lung. Rarely tiny calcific deposits (Simon’s foci) may be observed in other parts of the lung, they appear as round coin-like lesions on the X-ray.

Complications of the primary complex

In people with compromised immunity the course of the primary may be more severe and progressive with the development of different conditions which may complicate the primary complex:

  • Rupture of the focus into the space around the lungs (the pleural cavity)
    The primary focus is often located close to the pleura – a membrane which lines out the lungs. When the lesion becomes bigger it may involve pleura and cause its rupturing – as the result, bacteria and caseous material gets into the pleural space as a large pleural effusion. Sometimes this effusion may become purulent – tuberculous empyema develops.
  • Acute cavitation of the focus
    In other cases the large primary focus ruptures and opens into a bronchus, respectively, the caseous material is discharged by coughing. When it happens tuberculosis can spread and affect other parts of the lungs.

Progressive primary tuberculosis

Progressive primary tuberculosis is the advanced disease observed in young children and those who have impaired immunity. It is characterized by the rapid decline in a person’s well-being and the development of tuberculous pneumonia.

Symptoms suggestive of primary pulmonary  tuberculosis

  • Chronic cough for more than 3 weeks or the cough which progressively worsens, in children usually there is no or little sputum;
  • Weigh loss for more than 4 weeks or failure to thrive/gain weight;
  • Weakness, general malaise, fatigue lately;
  • Unexplained fever or raised temperature for more than a week;
  • Swollen enlarged lymph nodes;

Primary abdominal tuberculosis

Mycobacterium bovis can be transmitted to children through the infected milk. The primary lesion is located in the intestines and abdominal lymph nodes causing abdominal pain , nausea, vomiting and constipation.

Primary infection of the skin

The bacteria may enter the skin through a recent break or cut of the skin, typically the face, the lower leg and the feet  are involved. After the wound has healed, a skin in that region appears thickened with tiny yellow areas. The superficial lymph nodes appear enlarged (regional lymphadenitis). 

Treatment

Young children at the age of less than 5 years without any symptoms of the disease but who are known to be recently infected or are at increased risk of acquiring tuberculosis should receive isoniazid for 9 months.

Pulmonary tuberculosis in children should be treated with isoniazid, rifampin and pyrazinamide for 2 months, continued with isoniazid and rifampin for 4 months.