-IBIS-1.5.0-
tx
respiratory system
tuberculosis
diagnoses

definition and etiology

definition:
An acute or chronic infection caused by Mycobacterium tuberculosis and, rarely in the USA, by M. bovis.

etiology:
TB is characterized clinically by a lifelong balance between the host and the infection, in which pulmonary or extrapulmonary foci may reactivate at any time, even after long periods of latency; TB is characterized pathologically by the formation of tubercles made up of giant cell and epithelioid cells, by a tendency for fibrosis to occur, and by caseation, a unique form of nonliquefying necrosis.
Infection is primarily by inhalation; may contaminate the air in enclosed spaces for long periods of time. Bovine TB may be transmitted through contaminated milk. A non-sensitized host has no specific immunologic defense against TB.

signs and symptoms

signs and symptoms:
Asymptomatic at first; signs become apparent when lesion is large enough to be seen on x-ray.
• fever, malaise,weight loss are very gradual and often unnoticed
• cough: sputum scanty then progressively increases; is green and purulent; may be yellow in cases with less cavitation
• hemoptysis may be first symptom seen
• pleural or chest wall pain may occur
• dyspnea may occur
• chest x-ray usually first finding

lab findings:
• culture (takes up to 8 weeks)
• acid fast stain of sputum
• TB skin testing

course and prognosis

Infection usually begins in the lower middle lung fields. The bacilli can spread through lymph system to any other organ. With development of tuberculin hypersensitivity 4-10 weeks into illness, a small area of pneumonitis develops, multiplication of bacilli is inhibited at the initial and metastatic foci, and the infection is quickly arrested.
In 10% of people, active disease evolves within 1-2 yrs. In the remainder, foci of infection remain dormant but viable, with risk of reactivation, for the life of the host.
CNS TB, pleural TB, TB pericarditis, genitourinary TB, GI TB, TB peritonitis, miliary TB, are all secondary possibilities.

differential diagnosis

• lung cancer
• chronic bronchitis


footnotes