A comparison of the genes of M. tuberculosis complex (MTBC) in humans to MTBC in animals suggests humans did not acquire MTBC from animals during animal domestication, as researchers previously believed. Both strains of the tuberculosis bacteria share a common ancestor, which could have infected humans even before the Neolithic Revolution. Skeletal remains show some prehistoric humans (4000 BC) had TB, and researchers have found tubercular decay in the spines of Egyptian mummies dating from 3000 to 2400 BC. Genetic studies suggest the presence of TB in the Americas from about AD 100.Before the Industrial Revolution, folklore often associated tuberculosis with vampires. When one member of a family died from the disease, the other infected members would lose their health slowly. People believed this was caused by the original person with TB draining the life from the other family members.Although Richard Morton established the pulmonary form associated with tubercles as a pathology in 1689, due to the variety of its symptoms, TB was not identified as a single disease until the 1820s. Benjamin Marten conjectured in 1720 that consumptions were caused by microbes which were spread by people living in close proximity to each other. In 1819 René Laennec claimed that tubercles were the cause of pulmonary tuberculosis. J. L. Schönlein first published the name "tuberculosis" (German:  Tuberkulose) in 1832.
Symptoms may include chest pain and a prolonged cough producing sputum. About 25% of people may not have any symptoms (i.e. they remain asymptomatic). Occasionally, people may cough up blood in small amounts, and in very rare cases, the infection may erode into the pulmonary artery or a Rasmussens aneurysm, resulting in massive bleeding. Tuberculosis may become a chronic illness and cause extensive scarring in the upper lobes of the lungs. The upper lung lobes are more frequently affected by tuberculosis than the lower ones. The reason for this difference is not clear. It may be due to either better air flow, or poor lymph drainage within the upper lungs. Extrapulmonary
In 15–20% of active cases, the infection spreads outside the lungs, causing other kinds of TB. These are collectively denoted as extrapulmonary tuberculosis. Extrapulmonary TB occurs more commonly in people with a weakened immune system and young children. In those with HIV, this occurs in more than 50% of cases. Notable extrapulmonary infection sites include the pleura (in tuberculous pleurisy), the central nervous system (in tuberculous meningitis), the lymphatic system (in scrofula of the neck), the genitourinary system (in urogenital tuberculosis), and the bones and joints (in Pott disease of the spine), among others. A potentially more serious, widespread form of TB is called "disseminated tuberculosis", it is also known as miliary tuberculosis. Miliary TB currently makes up about 10% of extrapulmonary cases. Causes
Mycobacteria
The main cause of TB is Mycobacterium tuberculosis (MTB), a small, aerobic, nonmotile bacillus.