New approaches to the diagnosis of tuberculosis in childhood with special reference to neurotuberculosis

Bacteriological diagnosis of tuberculosis in childhood is often unsuccessful owing to the difficulty in obtaining suitable specimens. Many attempts have been made to diagnose tuberculosis immunologically but with very limited success. Positive tuberculin reactions may be the result of nonspecific sensitization while negative reactions occur in undernourished children. Serodiagnostic tests suffer from problems of specificity, even when very specific antigens are used, and are often least helpful in diagnostically difficult cases. Detection of antigen has proved to be of more value, especially with clean specimens such as cerebrospinal and pleural fluids. Detection of specific components ofMycobacterium tuberculosis by linked gas chromatography and mass spectroscopy is very sensitive and specific but the equipment is very costly. Detection of specific DNA sequences ofM. tuberculosis in specimens by use of labelled ‘DNA probes’ is rather insensitive although the sensitivity may be increased greatly by use of the polymerase chain reaction to amplify small amounts of the specific DNA. Non specific indicators of tuberculosis are generally unhelpful although the bromide partition test and assay of the enzyme adenosine deaminase in cerebrospinal fluid appear to be of value in the diagnosis of tuberculous meningitis. More research is required to develop a simple, specific and automated test for tuberculosis in childhood.     

Acute isoniazid neurotoxicity in childhood

Acute isoniazid (INH) poisoning is uncommon in children. Although most physicians are aware of INH hepatotoxicity, acute INH poisoning and its treatment are not well recognized. INH is increasingly being used to control the spread of tuberculosis, and physicians should know its potentially fatal effects. INH overdose is known to result in rapid onset of seizures, metabolic acidosis and prolonged obtundation. We report two cases of obtundation secondary to INH overdose that was immediately reversed by pyridoxine. Parenteral pyridoxine administration is an effective method in INH intoxication. The intravenous form of pyridoxine must be available in the emergency care units, and INH toxicity should be suspected in any patient with refractory seizures and metabolic acidosis.     

Cutaneous hypersensitivity reactions due to thiacetazone in the treatment of tuberculosis in Zambian children infected with HIV-I.

Tuberculosis is one of the most common infections in Zambian adults and children infected with HIV. In Africa, cutaneous hypersensitivity reactions attributed to thiacetazone during treatment of tuberculosis in adults infected with HIV-I have been well documented. This study monitored adverse drug reactions during treatment for tuberculosis over an 18 month period (1 April 1990 to 31 October 1991) in 237 children with a clinical diagnosis of tuberculosis (125 boys and 112 girls; 88/237 (37%) infected with HIV-I) and 242 control children (149 boys and 93 girls; 26/242 (11%) infected with HIV-I). Twenty two (9%) of the 237 children with tuberculosis developed hypersensitivity skin reactions during the course of treatment. Adverse skin reactions were seen more often in children infected with HIV than in those who were not (odds ratio 11.65, 95% confidence interval 3.07 to 34.88). These represented 19 (21%) of 88 children infected with HIV and three (2%) of 149 children not infected with HIV. These skin reactions occurred after a period of treatment ranging between two and four weeks among 14 children receiving the HST (isoniazid, streptomycin, thiacetazone) regimen and eight children receiving the HSTR (isoniazid, streptomycin, thiacetazone, rifampicin) regimen. Twelve (55%) of the 22 children who reacted adversely to treatment developed the Stevens-Johnson syndrome. All 12 of these children with the Stevens-Johnson syndrome were infected with HIV. The mortality among these children who developed the Stevens-Johnson syndrome was 91% (11 of 12 died within three days of the onset of the reaction). No further reactions were observed in the 11 children who recovered from the cutaneous hypersensitivity reactions after thiacetazone was discontinued over a period of six months of further treatment of tuberculosis. The results of this study were in part responsible for the recommendations put forward by the World Health Organization to avoid the use of thiacetazone in the treatment of tuberculosis in children infected with HIV.