• Infants + young children and the elderly.
• Usually secondary to other conditions associated with local
general defence mechanisms:
- viral infections (influenza, measles)
- aspiration of food or vomitus
- obstruction of a bronchus (foreign body or neoplasm)
- inhalation of irritant gases
- major surgery
- chronic debilitating diseases, malnutrition
Previously healthy individuals.
Unilateral stabbing chest pain on inspiration
(due to fibrinous pleurisy).
Pathology of lobar pneumonia:
Lasts < 24 hours: Alveoli filled with
oedema fluid and bacteria.
• Firm, 'meaty' and airless appearance of lung.
• Alveolar capillary dilatation.
• Strands of fibrin extending from one alveolus
another via inter-alveolar pores of Kohn.
• Also neutrophils in alveoli.
• Pleura: Fibrinous exudate.
Macrophages, neutrophils + fibrin
- Lysis and removal of fibrin via sputum +
- Begins after 8-9 days (without antibiotics).
- Sudden improvement of patient's condition.
Complications of lobar pneumonia
1. Abscess formation
3. Failure of resolution ⇒ intra-alveolar scarring
('carnification') ⇒ permanent loss of ventilatory
function of affected parts of lung.
- Infective endocarditis
- Cerebral abscess / meningitis
- Septic arthritis
• Common inhabitant of oral cavity (poor
• Lobar pneumonia in the elderly, diabetics,
alcoholics (aspiration of saliva).
Community acquired vs. nosocomial infection
- Often patients in ICU
- ↓ Local resistance to infection in lungs
- Intubation of respiratory tract
- Altered normal flora due to antibiotics
- E.coli, Klebsiella, Proteus, Pseudomonas,
Infection by usually non-pathogenic
- Pneumocystis carinii
- Other fungi
- Cytomegalovirus (CMV)
Fig. A viral pneumonia with interstitial lymphocytic
infiltrates. Note that there is no alveolar exudate.
Thus, the patient with this type of pneumonia will
probably not have a productive cough.
The most common causes for viral pneumonia are:
• Respiratory syncytial virus (RSV)
- appears mostly in children
- in immunocompromised hosts.
Fig. RSV accounts for many cases of pneumonia in children
under 2 years, and can be a cause for death in infants 1 to 6
months of age or older.
Localised area of suppuration and tissue