kelvinstudy
PNEUMONIA
Definition: Pneumonia is an acute respiratory lung illness that follows infection of the lung parenchyma
and produces distinct pathological and radiological features.
Classification
A. Clinical
1. Community acquired pneumonia (CAP) commonly due to:-
Strep. Pneumoniae
H. influenza (esp. elderly patients)
Mycoplasma pneumoniae and chlamydia pneumoniae especially in young
adults.
Viral infection especially in young children.
2. Hospital acquired (nosocomial) pneumonia commonly due to:-
Gm negative enterobacteriae e.g. E.coli, pseudomonas, Klebsiella.
Others –staph aureus, MRSA, anaerobic organisms.
3. Pneumonia in the immunocompromised host usually due to :-
Cmv
Pneumocystis jirovecii
Fungal pneumonias
4. Aspiration pneumonia commonly due to:-
Strep pneumonia
H. influenzae
Moraxella catarrhalis
B. Radiological / pathological
1. Lobar pneumonia- homogenous consolidation of one or more lung lobes, often with
assoc. pleural inflammation.
2. Bronchopneumonia- patchy alveolar consolidation assoc. with bronchial and bronchiolar
inflammation often affecting both lower lobes.
Risk factor for pneumonia:-
A. Host defenses- most pneumonia occur when the immune defenses are impaired as in:-
Loss or decreased cough reflex- GA, muscular disorders, drugs
Injury to muco-cilliary apparatus- smoking, hot or corrosive gases, infection- URTI,
recent influenza infection etc.
Use of bacteriocidal agents- alcoholism, tobacco smoking, oxygen intoxication
Pulmonary cong. and pulmonary oedema.
Defects in inmate immunity.
Accumulation of secretion as in cystic fibrosis.
B. Virulent organisms- type of micro-organism involved.
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C. Overwhelming dose of micro-organisms.
Routes of infection
Main route of infection is droplet inhalation (micro-inhalation) but haematogenous infections
can also occur.
Direct spread is rare.
COMMUNITY ACQUIRED PNEUMONIA
CAP affects about 5-11/1000 and accounts for 5% of the lower respiratory tract infection.
The incidence varies with age but CAP is more common in the young and the very old.
It accounts for 1/5 of the death of children (250 million) annually in the world.
Case-fatality rate in 2-10% but with virulent organisms, fatality can be as much as 50%.
Pathogenesis:-
CAP is acquired through droplet inhalation (micro-inhalation). The organisms are deposited in
the lung tissue →inflammation with four distinct features:
i. Congestion
ii. Red hepatization- massive exudation of RBCs, neutrophils and fibrin.
iii. Grey hepatization- PMNS invade affected site and phagocytose bacteria.
iv. Resolution- consolidated phase undergoes resolution /healing with little or no scarring.
Clinical features / presentation:-
Constitutional symptoms- usually acute onset with fever, rigors, headache, vomiting and
loss of appetite.
Pulmonary symptoms- cough: short painful cough, initially dry and later productive of
rusty sputum especially in strep pneumonia infections.
Pleuritic chest pain
Strep pneumonia accounts for over 80% of bacterial pneumonias especially in young
and middle aged patients. Commonly presents with fever, herpes labialis.
Bacteria pneumonias are usually worse in female patients and those with COPD.
Chlamydia pneumonia- common in the young and middle aged. Is usually mild and self-
limiting disease, has a long prodromol period. Diagnosed on serology.
Mycoplasma pneumonia- walking pneumonia; critically produces dry hacking cough in
an ambulatory patient. Peak age- young adults and children. Causes epidemics four
yearly. Causes unique cmxs:-
Haemolytic anaemia
Stevens Johnson syndrome
Erythema nodosum
Myocarditis, pericarditis
Guillian Barre syndrome
2
PNEUMONIA
Definition: Pneumonia is an acute respiratory lung illness that follows infection of the lung parenchyma
and produces distinct pathological and radiological features.
Classification
A. Clinical
1. Community acquired pneumonia (CAP) commonly due to:-
Strep. Pneumoniae
H. influenza (esp. elderly patients)
Mycoplasma pneumoniae and chlamydia pneumoniae especially in young
adults.
Viral infection especially in young children.
2. Hospital acquired (nosocomial) pneumonia commonly due to:-
Gm negative enterobacteriae e.g. E.coli, pseudomonas, Klebsiella.
Others –staph aureus, MRSA, anaerobic organisms.
3. Pneumonia in the immunocompromised host usually due to :-
Cmv
Pneumocystis jirovecii
Fungal pneumonias
4. Aspiration pneumonia commonly due to:-
Strep pneumonia
H. influenzae
Moraxella catarrhalis
B. Radiological / pathological
1. Lobar pneumonia- homogenous consolidation of one or more lung lobes, often with
assoc. pleural inflammation.
2. Bronchopneumonia- patchy alveolar consolidation assoc. with bronchial and bronchiolar
inflammation often affecting both lower lobes.
Risk factor for pneumonia:-
A. Host defenses- most pneumonia occur when the immune defenses are impaired as in:-
Loss or decreased cough reflex- GA, muscular disorders, drugs
Injury to muco-cilliary apparatus- smoking, hot or corrosive gases, infection- URTI,
recent influenza infection etc.
Use of bacteriocidal agents- alcoholism, tobacco smoking, oxygen intoxication
Pulmonary cong. and pulmonary oedema.
Defects in inmate immunity.
Accumulation of secretion as in cystic fibrosis.
B. Virulent organisms- type of micro-organism involved.
1
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C. Overwhelming dose of micro-organisms.
Routes of infection
Main route of infection is droplet inhalation (micro-inhalation) but haematogenous infections
can also occur.
Direct spread is rare.
COMMUNITY ACQUIRED PNEUMONIA
CAP affects about 5-11/1000 and accounts for 5% of the lower respiratory tract infection.
The incidence varies with age but CAP is more common in the young and the very old.
It accounts for 1/5 of the death of children (250 million) annually in the world.
Case-fatality rate in 2-10% but with virulent organisms, fatality can be as much as 50%.
Pathogenesis:-
CAP is acquired through droplet inhalation (micro-inhalation). The organisms are deposited in
the lung tissue →inflammation with four distinct features:
i. Congestion
ii. Red hepatization- massive exudation of RBCs, neutrophils and fibrin.
iii. Grey hepatization- PMNS invade affected site and phagocytose bacteria.
iv. Resolution- consolidated phase undergoes resolution /healing with little or no scarring.
Clinical features / presentation:-
Constitutional symptoms- usually acute onset with fever, rigors, headache, vomiting and
loss of appetite.
Pulmonary symptoms- cough: short painful cough, initially dry and later productive of
rusty sputum especially in strep pneumonia infections.
Pleuritic chest pain
Strep pneumonia accounts for over 80% of bacterial pneumonias especially in young
and middle aged patients. Commonly presents with fever, herpes labialis.
Bacteria pneumonias are usually worse in female patients and those with COPD.
Chlamydia pneumonia- common in the young and middle aged. Is usually mild and self-
limiting disease, has a long prodromol period. Diagnosed on serology.
Mycoplasma pneumonia- walking pneumonia; critically produces dry hacking cough in
an ambulatory patient. Peak age- young adults and children. Causes epidemics four
yearly. Causes unique cmxs:-
Haemolytic anaemia
Stevens Johnson syndrome
Erythema nodosum
Myocarditis, pericarditis
Guillian Barre syndrome
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