Tuberculosis in children

Tuberculosis (tb) is an infectious disease causes by a bacterium known as Mycobacterium tuberculosis. The disease is prevalent all over the world though more common in developing countries.

The disease usually spreads through droplets of secretions in air containing the organism. It primarily affects the lungs (Pulmonary tb). But the organism can spread through the blood stream and affect virtually every organ in the body.

Symptoms and signs: When the disease primarily affects the lungs the usual symptoms are cough and fever. As these symptoms can occur in any infection the disease is not distinguishable from other causes of respiratory infection.

Hence in countries where the disease is common it should be suspected in any child who does not respond to the usual treatment within about two weeks. Other features are loss of appetite and loss of weight.

Other manifestations of the disease are swelling in neck (due to lymph node involvement), chronic abdominal pain (if the disease affects the intestine or abdominal lymph nodes), pain and swelling of joints (tuberculous arthritis) and headache and vomiting if the child has tuberculous meningitis.

Diagnosis: The Mantoux test is widely used as the initial screening test in children. It is cheap and is quite useful if its limitations are understood. It tests whether the body is sensitized to the antigen of the causative organism.

The test consists of giving on injection of the antigen derived from the bacterium intra-dermally (into the layers of skin). It causes a small elevation at the site.

A negative test (no induration or induration of less than 10 mm at the site of injection) is extremely helpful in ruling out the disease provided the child has not received any immuno suppressive drug (like steroids), does not suffer from any immuno deficiency disease or from widely disseminated form of the disease.

If the patient is sensitized to the bacterium the body mounts an immune response against the antigen causing immune cells to accumulate at the site of injection. This causes an induration. An induration of 10mm or more is considered as significant.

Chest X-ray: This may not reveal any abnormality in very early stages. Later it may show opacities caused by inflammation in the lungs and enlargement of lymph nodes in the mediastinum. The changes are not specific and the diagnosis should be made after correlating all the clinical and other investigation.

Blood examination reveals elevation of erythrocyte sedimentation rate (ESR). White blood cell may be normal or show elevation of lymphocytes. ESR is a non specific marker of inflammation.

Biopsy: If lymph nodes are involved biopsy of the affected node can confirm the diagnosis.

Antibodies: Antibodies to the tubercle bacilli can be demonstrated in the blood. IgM class of anti-bodies indicate recent infection.

When tuberculous meningitis is suspected lumbar puncture should be performed and the cerebrospinal fluid examined.

It should be remembered that the diagnosis of tuberculosis is made after taking into consideration all the clinical and relevant investigations. Contact with a patient of tuberculosis especially one who has the organisms in the sputum is given considerable importance in decision making.

It is not always possible to isolate the organism by culture. Sputum examination cannot be done in small children and in older children it is usually negative. Sometimes it may be possible to demonstrate the organism in the gastric fluid but this too is usually negative.

Treatment: Unlike many other infections tuberculosis has to be treated with multiple drugs. The current practice is to start the child on a combination of 3 drugs except is very serious forms of the disease when 4 drugs are used initially. The preferred drugs are Rifampicin, Isoniazid and Pyrazinamide.

Three drugs regimen is given for 2 months. After 2 months the patient is given a combination of 2 drugs- rifampicin and Isoniazid. This regimen is given for another 4 months making up a total of 6 months of treatment.

In severe forms of the disease (tuberculos meningitis or miliary tuberculosis) another drugs is given for the first 2 month. The usual drug is Streptomycin. This has to be given as infection.

Liver function has to be monitored while the child is on antitubercular drugs as the drugs can damage the liver. Rifampicin causes red coloration of urine, tears and stool.

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