infectious diseases
Tuberculosis (TB)
Special Populations
Children infected with tuberculosis are more likely than adults to develop active disease, which commonly manifests as extrapulmonary disease. Lymphadenitis (scrofula) is the most common extrapulmonary manifestation, but TB may also affect the vertebrae ( Tuberculosis of bones and joints ), the highly vascular epiphyses of long bones, or the central nervous system and meninges. Clinical presentation of active TB in children varies, making the diagnosis challenging. Most children have few symptoms other than a brassy cough. Obtaining a sample for culture often requires one of the following: Gastric aspiration Sputum induction A more invasive procedure such as bronchoalveolar lavage The most common sign on chest x-ray is hilar lymphadenopathy, but segmental atelectasis is possible. Adenopathy may progress, even after chemotherapy is started, and may cause lobar atelectasis, which usually clears during treatment. Cavitary disease is less common than in adults, and most children harbor far fewer organisms and are not contagious. Treatment strategies are similar to those for adults except that drugs must be dosed strictly based on the child's weight (see table). Reactivated disease can involve any organ but particularly the lungs, brain, kidneys, long bones, vertebrae, or lymph nodes. Reactivation may cause few symptoms and can be overlooked for weeks or months, delaying appropriate evaluation. The frequent presence of other disorders in old age further complicates the diagnosis. Regardless of their age, nursing home residents who previously had a negative TST are at risk of disease due to recent transmission, which may cause apical, middle-lobe, or lower-lobe pneumonia as well as pleural effusion. The pneumonia may not be recognized as TB and may persist and spread to other people while it is being erroneously treated with ineffective broad-spectrum antibiotics. In the US, miliary TB and TB meningitis, commonly thought to affect mainly young children, are more common among older people. Risks and benefits of preventive treatment should be carefully assessed before older people are treated. INH causes hepatotoxicity in up to 4 to 5% of patients>65 years old (compared with<1% of patients<65 years old). As a result, chemoprophylaxis is usually given to older people only if the induration after TST increases≥15 mm from a previously negative reaction. Close contacts of an active case and others at high risk and with a negative TST or IGRA result should also be considered for preventive treatment unless contraindicated. TST sensitivity is generally poor in immunocompromised patients, who may be anergic. In some studies, IGRAs appear to perform better than the TST in immunocompromised patients, although this advantage has not yet been established. In patients with untreated Human Immunodeficiency Virus (HIV) Infection and latent tuberculosis infection (LTBI), active TB develops in about 10%/year, whereas in people who are not immunocompromised, it develops in about the same percentage over a lifetime. In the early 1990s, half of patients coinfected with TB and HIV who were untreated or infected with a multidrug-resistant strain died, with median survival of only 60 days. Now, outcomes are somewhat better in countries where there is better testing and treatment because of earlier TB diagnosis and antiretroviral therapy, but TB in patients with HIV remains a serious concern. In countries with limited access to drugs and testing for TB and HIV infection, mortality continues to be high among patients coinfected with HIV and multidrug-resistant TB or extensively drug-resistant TB. Dissemination of bacilli during primary infection is usually much more extensive in patients with HIV infection. Consequently, a larger proportion of TB is extrapulmonary. Tuberculomas (mass lesions in the lungs or central nervous system due to TB) are more common and more destructive. HIV infection reduces both inflammatory reaction and cavitation of pulmonary lesions. As a result, a chest x-ray may show a nonspecific pneumonia or even be normal. Smear-negative TB is more common when HIV coinfection is present. Because smear-negative TB is common, HIV-TB coinfection is often considered a paucibacillary disease state. complex ( Nontuberculous Mycobacterial Infections ). Infection with MAC is not contagious and, in patients with HIV infection, affects primarily the blood and bone marrow, not the lungs. Patients with HIV infection who were not diagnosed before presenting with TB should receive 2 weeks of antimycobacterial treatment before starting antiretroviral therapy to decrease the risk of developing the Immune reconstitution inflammatory syndrome (IRIS) (IRIS). TB in patients with HIV infection generally responds well to usual regimens when in vitro testing shows drug susceptibility. However, for multidrug-resistant TB strains, outcomes are not as favorable because the drugs are more toxic and less effective. Therapy for susceptible TB should be continued for 6 to 9 months after sputum cultures convert to negative but may be shortened to 6 months if 3 separate pretreatment sputum smears are negative, suggesting a low burden of organisms. Current recommendations suggest that if the sputum culture is positive after 2 months of therapy, treatment is prolonged to 9 months. Patients with HIV infection whose tuberculin reactions are≥5 mm (or with a positive IGRA result) should receive chemoprophylaxis. CurrentCDC TB treatment guidelinesshould be consulted. 