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Gulf War and Health: Volume 5. Infectious Diseases
Late Manifestations of Pulmonary Tuberculosis
It is well accepted in the biomedical community that disability occurs after pulmonary TB. The most common adverse health outcomes are chronic disabling scarring of the lungs, long-term pulmonary dysfunction, secondary infection of residual cavities, empyema, bronchiectasis, bronchopleural fistulas, and aspergilloma. Rarely, scar carcinoma occurs. Despite the centuries-old history of TB, however, the published data on long-term manifestations are inadequate for the committee to comment on their duration, range, or severity of adverse health outcomes.
A number of studies have compared pulmonary function tests (PFTs) at diagnosis of and after treatment for active TB. For instance, a study of 25 TB patients in Canada found abnormal PFTs (reduced 1-second forced expiratory volume and forced vital capacity) in individuals with cavitary TB but not in those with noncavitary TB (Long et al. 1998). Another study, of 74 TB patients in South Africa, showed a restrictive lung function pattern in 57% of cases and an obstructive lung function pattern in 11%. After treatment for TB, 53% of patients still had abnormal PFTs (Plit et al. 1998). Although neither study commented on the potential disability associated with the findings, none of the patients had residual impairment of oxygenation at rest.
Multiple case reports have been published of patients who have developed “scar cancer”, lung cancer associated with lung scars from TB or other causes (Ardies 2003). The risk of cancer after TB has not been quantified, nor has the percentage of TB patients left with pulmonary scarring. One report from Japan indicated a 2% prevalence of lymphoma of the pleural space among patients with chronic pyothorax, which is associated with tuberculosis (Iuchi et al. 1987). Because pyothorax is a rare complication of TB, the authors could not quantify the overall risk of cancer posed by TB. In summary, the available data are insufficient for the committee to determine whether an association exists between cancer and active TB. If such an association does exist, cancer is undoubtedly a very rare consequence of TB.
Late Manifestations of Extrapulmonary Tuberculosis
The long-term adverse health outcomes of extrapulmonary TB occur with varied frequency depending on the site of active disease. The more common forms of extrapulmonary TB, pleural and lymphatic disease, rarely have long-term adverse health outcomes. Two of the less common forms, TB meningitis and skeletal TB, are more likely to result in irreversible tissue damage. In general, estimates of the long-term prognoses for uncommon forms of TB are based on relatively small series of patients.
Tuberculosis Meningitis and Long-Term Neurologic Disability
It is well accepted in the biomedical community that TB meningitis is associated with long-term neurologic outcomes. The extent of disability depends on the duration and severity of acute symptoms, the age of the patient, and the neurologic deficits (Dube et al. 1992; Kennedy and Fallon 1979). Of TB meningitis patients with stupor or dense paraplegia or hemiplegia, about half either die or recover with severe residual neurologic deficits (Kennedy and Fallon 1979). Until the 1990s, most reports of outcomes for adult patients with TB meningitis focused on mortality. As the recovery rate increased, more studies about the long-term prognoses for these patients emerged. Table 5.7 summarizes the findings of seven studies about long-term neurologic deficits of TB meningitis.