Lec 3 Pulmonary infections II Flashcards
Genetic makeup of MB TB:
-Linked to SLC11A1 (NRAMP1) polymorphism
Pathogenisis of MB TB:
-TB bacilli taken by alveolar macrophages thru action of mannose and compliment receptors.
-Bacilli inhibit phagolysosomal function
-they proliferate inside alveolar macrophages then released—- bacteremia
**-CD4+TH1 subset—- IFN gamma activate macrophages, which release TNF and chemokines—- bacterial killing
**
-Immune response leads to caseation (tissue necrosis)
Types of TB infection: 1) primary TB
-Ghon Focus- subpleural caseating granuloma
-Enlarged hilar LN with caseation (Ghon complex) (Gohn focus +Nodal involvement)
arises in unsensitized host or Immunocompromized
Signs and symptoms of MB TB:
Early symptoms:
* Common cold
* listlessness, fatigue and fever
* cough with yellow or green sputum
* Malaise
Later symptoms:
* Night sweats
* weight loss and fever
* hemoptysis
* dyspnea, hoarsness of voice due to reaching larynx
Outcome of primary TB:
-In 95% cell mediated immunity, healing in 3 weeks
-Fibrosis+ calcification= Ranke complex
-Progressive primary TB- uncommonly dissemenated disease
Location of 2ndary TB:
-at apex 2cm in size
-Cavitation is common
-Lymph node enlargment is LESS prominent
-Sputum is positive for TB bacilli
2) Secondary ( reactivation TB)
Arises in sensitized hosts in:
1)progressive post primary
2)Reactivation of old focus
3)reinfection with a virulent strain
Symptoms of 2ndary TB:
-Hemoptysis, fever, weight loss, night sweats
-Extra pulmonary manifestations
-may be asymptomatic
Outcome- can heal or become progressive
3)Progressive pulmonary TB
-Occurs at tracheobronchial tree and lymphatics
-pleural involvment—- empyema
-can spread to larynx, heart, intestine
4)Systemic milliary TB
Numerous tiny tubercles in any organ, most affected are:
(Liver, BM spleen, adrenal, meninges, kidenys)
5)Isolated organ TB
-spread thru blood
-symptoms depend on organ
i.e infertility- male genital system
-Vertebral TB- POTTS disease
-Adrenal Gland-Addisons disease
-TB scrofula- lymphadenitis
Chronic TB— secondary amyloidosis
Tuberculosis in HIV:
-In late stages— secondary TB reactivation, milliary and Atypical TB
-M.avium is common in late stages– poorly formed granuloma without caseation
Diagnosis of TB:
-Xray
-Sputum-Acid fast bacilli (ZN stain, PCR)
Skin test: PPD mantoux test
-Hypersensitivity to bacilli indicated, needs to be 5mm in diameter to be positive.
-false negative in milliary TB, hodgkin lymphoma, malnutrition
-False positive in atypical mycobacterial infection
Chronic pneumonias lesion:
very similar pathology to TB
Lesion is granuloma with necrosis and giant cells
