EXTRAPULMONARY TUBERCULOSIS. HamidReza Naderi MD Department of Infectious Diseases Mashhad University of Medical Sciences.
HamidReza Naderi MD
Department of Infectious Diseases
Mashhad University of Medical Sciences
Extrapulmonary TB, like pulmonary TB, is the result of infection with organisms of the Mycobacterium tuberculosis complex, which include M. tuberculosis, Mycobacterium bovis or Mycobacterium africanum.
Extrapulmonary TB is defined as disease involving structures other than lung parenchyma and is less common than pulmonary TB.
Extrapulmonary tuberculous disease occurs as result of contiguous spread of tubercle organisms to adjoining structures, such as pleura or pericardium, or by lymphohaematogenous spread during primary or chronic infection.
According to the World Health Organization (WHO) patients who are sputum smear-positive and also present with extrapulmonary tuberculous disease manifestations are categorized as pulmonary TB.
Extrapulmonary TB may occur in multiple sites, with relative frequencies of 42% for lymphatic, 18% for pleural, 12% for bone or joint, 6% for genitourinary, 6% for meningeal, 5% for peritoneal, and 11% for other sites.
The lymph nodes are the most common site of extrapulmonary TB for both otherwise normal and HIV-infected patients.
Involvement of the meninges is more common in young children than in other age groups (present in approximately 4% of children with TB), and the incidence of TB in the remainder of the extrapulmonary sites increases with age.
The diagnosis usually is confirmed by microscopic and chemical examination of pleural fluid or pleural biopsy.
Bone and Joint InfectionBone and joint TB remains a disease of older children and young adults in developing countries.Skeletal TB presumably develops from reactivation of dormant tubercles originally seeded during stage 2 of the primary infection or, in the case of spinal TB, from contiguous spread from paravertebral lymph nodes to the vertebrae.Generally, spinal TB (Pott's disease) accounts for 50 to 70% of the reported cases; the hip or knee is involved in 15 to 20% of cases, and the ankle, elbow, wrists, shoulders, and other bones and joints account for 15 to 20% of cases.
Paraspinal “cold” abscesses develop in 50% or more of cases, with occasional formation of sinus tracts.
The most common clinical manifestations of gastrointestinal TB are abdominal pain, fever, weight loss, anorexia, nausea, vomiting, and diarrhea.
The peritoneal fluid is exudative, with a cell count of 500 to 2000 cells per mL. Lymphocytes usually predominate, with rare exceptions early in the process, when polymorphonuclear leukocytes may predominate.
AFB smears of the fluid have a low diagnostic yield, with a reported sensitivity of no more than 7%, and the culture result is positive in only 25% of the cases. Peritoneal biopsy often is necessary to confirm the diagnosis.
Extrapulmonary foci usually respond to treatment more rapidly than does cavitary pulmonary tuberculosis due to the lower burden of organisms in the former.
In lymph node TB, the most common form of extrapulmonary TB, the affected nodes may enlarge while patients are receiving appropriate therapy and even after completion of therapy without evidence of bacteriological relapse.