Clinical Manifestations and Pathology

Tuberculosis most commonly infects the lungs, but it can infect almost any other part of the body, and frequently causes disease in the meninges, intestines, bones, lymph glands surrounding the neck, skin, spine, kidneys, and genitals. Most of these forms, with the exception of tubercular meningitis, are chronic, taking months and sometimes years before resulting in either recovery or death. Miliary tuberculosis concurrently affects almost every vital organ.

Because pulmonary tuberculosis is by far the most common form of this disease, it usually brings to mind its most familiar symptom: an increasingly frequent and violent cough that produces a purulent sputum sometimes streaked with blood. Coughing up larger amounts of blood hemorrhaged in the lungs is not uncommon in advanced cases, but this is by no means a universal symptom. Indeed, until the disease reaches its advanced stages, many victims are completely free of symptoms or experience only the mild respiratory symptoms similar to those of influenza or a common cold. The systemic symptoms of tuberculosis generally include fatigue, lethargy, anorexia, weight loss, irregular menses, ill-defined anxiety, chills, muscular aches, sweating, and low-grade fevers that continue indefinitely. In the past, however, many people developed mild or even asymptomatic cases of the disease and recovered before realizing it, as autopsies, and later X-rays, revealed.

Because in its early stages tuberculosis has only unalarming symptoms and myriad possible manifestations, diagnosis is difficult even today. Preliminary diagnosis can be made with a tuberculin test, which usually indicates whether a person has become infected with the tubercle bacillus. On the other hand, although tuberculin testing is highly reliable today, false-positive responses are not unknown.

The tubercle bacillus by itself does not damage the normal human body; it neither contains nor exudes any toxic materials. Rather cellular and tissue damage arises from an allergic reaction in the body, or hypersensitivity, which occurs in response to contact with the bacillus. In other words, after the body has become allergic to invading tubercle bacilli, the immune system destroys them. This process, however, releases proteins and fatty substances that in turn can cause inflammation and can damage surrounding tissue and cells. This same process also creates the tubercles that distinguish the disease. Experts sometimes refer to tubercles as caseous areas because they often have a cheesy consistency, although they can become as hard as rocks. Alternatively, caseous areas can liquefy, leaving a cavity. If this occurs close to a major blood vessel, it may result in a hemorrhage.

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