In the early 20th century in the United States, when tuberculosis was more prevalent, the risk of becoming infected with M. tuberculosis was high across the entire population. Currently, tuberculosis has retreated into fairly well-defined pockets of high-risk individuals, such as foreign-born persons from high-prevalence countries, persons who travel to high-prevalence countries, inmates of correctional institutions, illicit drug users, unprotected health care workers who care for high-risk patients, migrant families, homeless persons, and anyone likely to encounter people with contagious tuberculosis. One must distinguish the risk factors for becoming infected with M. tuberculosis from factors that increase the likelihood that an infected individual will develop disease. Age, immunocompromised status, and recent infection with M. tuberculosis are the major risk factors for progression of infection to disease.
Although tuberculosis occurs throughout the United States, cases are disproportionately reported from large urban areas. Cities with populations exceeding 250,000 account for only 18% of the U.S. population, but almost 50% of tuberculosis cases in the United States. Among U.S.-born persons, tuberculosis disproportionately affects African Americans, whose rates of tuberculosis disease remain 8.5 times the rates seen in whites born in the United States [31,32].
The number of tuberculosis cases in the United States is increasing among foreign-born persons from countries with a high prevalence of tuberculosis. The percentage of total cases of tuberculosis in the United States that occurs in foreign-born individuals increased from 22% in 1986 to 59% in 2007, and foreign-born individuals have a 9.7 times higher rate of tuberculosis than individuals born in the United States [31]. In addition, 85% of cases of multidrug-resistant [MDR] tuberculosis are seen in foreign-born individuals [31]. In previous estimates, two thirds of foreign-born individuals with tuberculosis were younger than 35 years when entering the United States, and in many cases, their disease could have been prevented if they had been identified as infected after immigration and given appropriate treatment for M. tuberculosis infection.
Until very recently, new immigrants to the United States older than 15 years of age were required to have a chest radiograph but no tuberculin skin test to detect asymptomatic infection; children younger than 15 years old received no tuberculosis testing as part of immigration [33]. This policy ignored a huge reservoir of future tuberculosis cases. Studies have estimated that 30% to 50% of the almost 1 million annual new immigrants to the United States are infected with M. tuberculosis [29]. Foreign-born women and adolescents of childbearing age should be one group targeted for appropriate tuberculosis screening and prevention [34]. There are data suggesting that the current U.S. Centers for Disease Control and Prevention [CDC] and American Thoracic Society [ATS] policies on targeted screening of immigrants [35] would fail to prevent most cases [36]. A more effective strategy to decrease tuberculosis in the United States may be to expand treatment programs in countries from which immigrants originate [37].
Another factor that has had a great impact on tuberculosis case rates in the United States has been the epidemic of HIV infection [27]. The proportion of women with HIV infection is increasing; the population demographic in which HIV is most rapidly spreading is persons of reproductive age [13 to 44 years old], who accounted for 73% of newly diagnosed cases in 2006 [38]. Because the risk factors for HIV infection intersect with risk factors for tuberculosis, the number of coinfected women is expected to increase [39–41]. Approximately 16% of tuberculosis patients 25 to 44 years old in the United States are also HIV-seropositive [42]. In most locales experiencing increases in tuberculosis cases, the demographic groups with the greatest tuberculosis morbidity rates are the same as those with high morbidity rates from HIV infection. HIV-infected persons with a reactive tuberculin skin test develop tuberculosis at a rate of 5% to 10% per year compared with a historical average of 5% to 10% for the lifetime of an immunocompetent adult. There is controversy concerning the infectiousness of adults with HIV-associated pulmonary tuberculosis. Although some studies have indicated dually infected adults are as likely as non–HIV-infected adults with tuberculosis to infect others, some studies have shown less transmission from HIV-infected adults [43].
The current epidemiology of tuberculosis in pregnancy is unknown. From 1966-1972, the incidence of tuberculosis during pregnancy at New York Lying-In Hospital ranged from 0.6% to 1% [44]. During this time, 3.2% of the patients with culture-proven pulmonary tuberculosis were first diagnosed during pregnancy, a rate equal to that of nonpregnant women of comparable age. Only two series of pregnant women with tuberculosis have been reported from the United States in the past 2 decades [45,46], and two series have been reported from the United Kingdom [47,48]. In the latter two series, diagnosis was delayed in many women with extrapulmonary manifestations of tuberculosis. Increased risk of tuberculosis is most striking for foreign-born women, who have high rates of tuberculosis infection, and poor minority women.
In the United States, almost 40% of tuberculosis cases in minority women occur in women younger than 35 years. Approximately 80% of cases of tuberculosis infection and disease among children in the United States occur in minority populations [25,49]. Most of these cases occur after exposure to an ill family member. In all populations, whether the disease incidence is high or low, tuberculosis infection and disease tend to occur in clusters, often centered on the close or extended family, meaning that minority newborns are at greatly increased risk of congenital and postnatally acquired tuberculosis infection and disease.
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Tuberculosis : Clinical Manifestations and Diagnosis
V. Courtney Broaddus MD, in Murray & Nadel's Textbook of Respiratory Medicine, 2022
Radiographic Features
Radiographic examination of the chest is commonly the first diagnostic study undertaken, after the history and physical examination.16,17 However, in resource-limited settings, a chest radiograph is not necessarily included as part of the routine evaluation because of cost, complexity, and nonspecificity of the findings.18
Pulmonary TB nearly always causes detectable abnormalities on the chest radiograph, although, in patients with HIV infection, a chest radiograph may be normal in up to 11% of patients with positive sputum cultures, and the chest radiograph may be normal in laryngeal TB.
Inprimary TB, resulting from recent infection, the process is generally seen as a middle or lower lung zone opacity, often associated with ipsilateral hilar adenopathy [Fig. 53.1]. Atelectasis may result from compression of airways by enlarged lymph nodes. If the primary process persists beyond the time when specific cell-mediated immunity develops, cavities may form [so-called progressive primary TB].
Inreactivation TB, developing at a time remote from the original infection, one sees involvement of the upper lobes of one or both lungs. Cavitation is common in this form of TB. The most frequent sites are the apical and posterior segments of the right upper lobe [Fig. 53.2] and the apical-posterior segment of the left upper lobe. Healing of the tuberculous lesions usually results in development of a fibrotic scar with shrinkage of the lung parenchyma and, often, calcification. Involvement of the anterior segments alone is unusual. In the immunocompetent adult with TB, intrathoracic adenopathy is uncommon. When the disease progresses, infected material may be spread via the airways [i.e., “bronchogenic” spread] into the lower portions of the involved lung or to the other lung. Erosion of a parenchymal focus of TB into a blood or lymph vessel may result in dissemination of the organism and a miliary pattern on chest imaging [Fig. 53.3; seeFig. 20.21]. Radiographic findings in HIV-infected patients are affected by the degree of immunosuppression. As further explained and illustrated inChapter 123, TB early in the course of HIV infection—before profound depletion of CD4 T cells—tends to produce typical radiographic findings with predominantly upper lobe infiltration and cavitation.20 With more advanced HIV disease and CD4 T-cell deficiency, the radiographic findings become more “atypical”: cavitation is uncommon, and lower lung zone or diffuse opacities and intrathoracic adenopathy are frequent [Fig. 53.4]. Surprisingly, a substantial number of HIV-infected patients with pulmonary TB have normal radiographs at the end of their course of treatment.21
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Tuberculosis
Geetha Ramachandran, Soumya Swaminathan, in Handbook of Pharmacogenomics and Stratified Medicine, 2014
36.2 TB Etiology and Natural History
Tuberculosis is caused by the bacillus Mycobacterium tuberculosis [Figure 36.1] [3]. It typically affects the lungs [pulmonary TB] but can affect other sites as well [extrapulmonary TB]. The disease is spread in the air when people who are sick with pulmonary TB expel bacteria, for example by coughing. In general, a relatively small proportion of people infected with Mycobacterium tuberculosis will develop TB disease; however, the probability of developing TB is much higher among people infected with HIV. TB is also more common among men than women and affects mostly adults in economically productive age groups.
Figure 36.1. Causative organism for TB.
High-power micrograph of acid-fast bacilli in the sputum of a patient with tuberculosis, shown by Ziehl-Neelsen staining [×1000].
Source: Reproduced with permission from Lawn and Zumla [3].The natural history of TB is influenced by several factors, the course being determined by the balance between host immunity and virulence of the TB bacillus. This understanding facilitates identification of areas where interventional strategies can be identified for TB control [4–6].
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Tuberculosis
Javad Parvizi MD, FRCS, ... Associate Editor, in High Yield Orthopaedics, 2010
Definition:
Tuberculosis [TB] is an inhaled infectious disease that primarily affects the lungs; however, it may also affect the central nervous system, lymphatic and circulatory systems, bones, and tissues. TB was the cause of the “white plague” in the seventeenth and eighteenth centuries in Europe.
Incidence:
Eight million people globally develop TB and 3 million die from the disease. In 1998, there were about 18,000 new cases in the United States.
Age and Gender:
TB is not age or gender specific.
Etiology and Pathophysiology:
Tuberculosis is caused by an acid-fast, aerobic bacilli bacterium—Mycobacterium tuberculosis. The disease is initiated when the bacilli reach the pulmonary alveoli after inhalation. TB is a granulomatous inflammatory condition causing periods of tissue destruction and necrosis followed by healing and fibrosis.
Associations and Predispositions:
Infection with human immunodeficiency virus, acquired immunodeficiency syndrome, poor nutrition and environmental conditions, intravenous drug use, and alcoholism.
Fig. 226-1. Magnetic resonance imaging study showing extensive destruction of L1 and L2 vertebral bodies and the intervening disk with posterior extension in a Pakistani man with Pott’s disease.
[From Mandell GL, Bennett JE, Dolin R [eds.]: Principles and Practice of Infectious Diseases, 6th ed. Philadelphia, Saunders, 2005.]Signs and Symptoms:
Signs and symptoms include a persistent dry cough, significant weight loss, a decrease in energy, fever, and night sweats. For advanced stage tuberculosis, symptoms include chest pain and difficulty breathing.
Diagnostic Studies:
Diagnostic tests include chest x-ray examination, computed tomography scan, sputum cultures, tuberculin skin test, bronchoscopy, interferon [IFN]-gamma blood test, and QuantiFERON-TB Gold, which has more recently been used instead of the tuberculin skin test.
Macropathology:
An individual with stage IV TB disease presents with either exudative lesions resulting from polymorphonuclear leukocytes around M.tuberculosis or granulomatous lesions due to hypersensitivity of the host to tuberculoproteins. These lesions appear in the well-aerated upper lobes of the lungs because M. tuberculosis is an obligate aerobe.
Micropathology:
Once M. tuberculosis is inhaled, activated macrophages surround tubercles; this complex often serves as a breeding ground, hence promoting growth of M. tuberculosis.
Treatment:
If active TB is diagnosed or strongly suspected, treatment is initiated with isoniazid, rifampin, pyrazinamide, and ethambutol. Dosage and drug of choice are altered per case, gender, and age. Second-line drugs include cycloserine, ethionamide, streptomycin, and levofloxacin.
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Tuberculosis
Ann M. Loeffler MD, in Pediatric Clinical Advisor [Second Edition], 2007
Basic Information
Definition
Tuberculosis [TB] is a disease characterized by active replication of Mycobacterium tuberculosis complex. Children with pulmonary TB have chest radiographic changes and may or may not have clinical symptoms or physical examination abnormalities. Latent TB infection [LTBI] is an infection with M. tuberculosis, but the organism is in a latent or dormant state. The patient has a skin test result that is positive for TB but a normal chest radiograph and no signs or symptoms of tuberculosis.
Synonyms
Consumption
LTBI
Scrofula [i.e., mycobacterial disease in a peripheral lymph node]
TB
010.01 Primary tuberculosis [often used to code for LTBI]
011.6 Tuberculosis pneumonia [any form]
012.1 Tuberculosis of intrathoracic lymph nodes
017.2 Peripheral scrofula
795.5 Positive tuberculosis TB skin test [TST] without active tuberculosis [nonspecific]
V01.1 Exposure to active tuberculosis
Epidemiology & Demographics
•One third of the world's population is infected with M. tuberculosis.
○Incidence is highest in Asia, Africa, Eastern Europe, and Latin America.
○Prevalence of infection increases incrementally with age [i.e., with accumulated risk of exposure].
•Active tuberculosis after infection is highest in the first year of life.
○Children younger than 1 year old have a 40% risk of developing active disease if infected.
○This is in contrast to the population as a whole, who have only a 10% lifetime risk of reactivation to active disease.
•Other populations at increased risk of activation after infection:
○Adolescents [especially girls]
○Recently exposed or infected individuals [50% of the risk of activation is in the first 2 years of infection]
○Recent immigrants [