Paediatrics: Mycobacteria

Mycobacteria

Pulmonary tuberculosis

Pulmonary tuberculosis due to Mycobacterium tuberculosis.

Atypical mycobacterial infection could be the cause of the following:

•   Persistent lymphadenopathy: this infection is diagnosed after histology of a surgically resected node.

•   Disseminated infection in the immunocompromised patient. Mycobacterium avium intracellulare: is an infection often seen in patients with advanced disease due to HIV.

Tuberculous meningitis (TBM)

TBM is the most feared complication of M. tuberculosis infection.

•   Timing: usually occurs within 12mths of first infection.

•   Age group: most frequently occurs in those <5yrs of age.

•   Pathology: the initial pathology is occult haematogenous dissemination to the cerebral cortex from a p site (e.g. gut, lung). This increases in size until it reaches the meninges and subarachnoid space. A thick gelatinous exudate is created especially around the brainstem so that cranial nerves III, IV, and VI are commonly compromised. Hydrocephalus is common.

•   Clinical course: the onset is insidious and is characterized by apathy or disinterest, then intermittent headaches and anorexia. Fever is almost always present. Vomiting occurs in 50%. Focal neurological signs, seizures, or severely depressed conscious level may occur.

•   Diagnosis: 50% will grow Mycobacteria from their CSF and the Mantoux or gamma interferon release assay often positive. 40–90% have CXR changes of pulmonary disease.

•   Prognosis: most survive if treated in the early insidious stage. There is a very high complication rate, especially if the focal neurological signs are present at the start of therapy.

Treatment: therapy with four antituberculous agents and corticosteroids is for at least 12mths and should be supervised by a specialist team.