_🔹PATTERNS OF INFECTION_ ▪️Mycobacteria have mycolic acids in their outer cell wall which makes them resistant to quick immune destruction. ▪️Mycobacteria typically produce an adaptive immune response with an inflammatory reaction characterized as granulomatous inflammation,which can continue for weeks to months to years, depending upon the host response. ▪️A robust TH1 adaptive cell-mediated immune response is more effective than a TH2 response. ▪️In persons who are healthy,infection may be subclinical and inapparent,detected only by testing for evidence of an immune response. _🔹THERE ARE TWO MAJOR PATTERNS OF DISEASE WITH MYCOBACTERIUM TUBERCULOSIS:_ _🔹PRIMARY TUBERCULOSIS_ ▪️Seen as an initial infection,typical for infection in children. ▪️The initial focus of infection is a small subpleural granuloma accompanied by granulomatous hilar lymph node infection. ▪️Together,these make up the Ghon complex. ▪️In most cases,these granulomas resolve and there is no further spread of the infection. _🔹SECONDARY TUBERCULOSIS_ ▪️Seen mostly in adults as a reactivation of previous infection (or reinfection),particularly when health status declines. ▪️The granulomatous inflammation is much more florid and widespread. ▪️Typically,the upper lung lobes are most affected,and cavitation can occur. ▪️When resistance to infection is particularly poor, a "miliary" pattern of spread can occur in which there are a myriad of small millet seed (1-3 mm) sized granulomas, either in lung or in other organs. ▪️Dissemination of tuberculosis outside of lungs can lead to the appearance of a number of uncommon findings with characteristic patterns: _🔹SKELETAL TUBERCULOSIS_ ▪️Tuberculosis osteomyelitis involves mainly the thoracic and lumbar vertebrae (known as Pott disease) followed by knee and hip. ▪️There is extensive necrosis and bony destruction with compressed fractures (with kyphosis) and extension to soft tissues,including psoas "cold" abscess. _🔹GENITAL TRACT TUBERCULOSIS_ ▪️Tuberculous salpingitis and endometritis result from dissemination of tuberculosis to the fallopian tube that leads to granulomatous salpingitis,which can drain into the endometrial cavity and cause a granulomatous endometritis with irregular menstrual bleeding and infertility. ▪️In the male, tuberculosis involves prostate and epididymis most often with non-tender induration and infertility. _🔹URINARY TRACT TUBERCULOSIS_ ▪️A "sterile pyuria" with WBC's present in urine but a negative routine bacterial culture may suggest the diagnosis of renal tuberculosis. ▪️Progressive destruction of renal parenchyma occurs if not treated. ▪️Drainage to the ureters can lead to inflammation with ureteral stricture. _🔹CNS TUBERCULOSIS_ ▪️A meningeal pattern of spread can occur,and the cerebrospinal fluid typically shows a high protein,low glucose,and lymphocytosis. ▪️The base of the brain is often involved, so that various cranial nerve signs may be present. ▪️Rarely,a solitary granuloma,or "tuberculoma",may form and manifest with seizures or mass effect. _🔹GASTROINTESTINAL TUBERCULOSIS_ ▪️This is uncommon today because routine pasteurization of milk has eliminated Mycobacterium bovis infections. ▪️However,M. tuberculosis organisms coughed up in sputum may be swallowed into the GI tract. ▪️The classic lesions are circumferential ulcerations with stricture of the small intestine. ▪️There is a predilection for ileocecal involvement because of the abundant lymphoid tissue and slower rate of passage of lumenal contents. _🔹ADRENAL TUBERCULOSIS_ ▪️Spread of tuberculosis to adrenals is usually bilateral, so that both adrenals are markedly enlarged. ▪️Destruction of cortex leads to Addison disease. _🔹SCROFULA_ ▪️Tuberculous lymphadenitis of the cervical nodes may produce a mass of firm, matted nodes just under the mandible. ▪️There can be chronic draining fistulous tracts to overlying skin. ▪️This complication may appear in children, and Mycobacterium scrofulaceum may be cultured. _🔹CARDIAC TUBERCULOSIS_ ▪️The pericardium is the usual site for tuberculous infection of heart. ▪️The result is a granulomatous pericarditis that can be hemorrhagic. ▪️ If extensive and chronic, there can be fibrosis with calcification,leading to a constrictive pericarditis.