Pneumonia ( Legionella pneumonia or Legionnair's disease )

Legionella pneumonia or Legionnair's disease

It is a epidemic disease caused by gram-negative bacilli, legionella pneumophila that thrives in aquatic environment. It was first recognised in those person that attending American legion convention in Philadelphia in july 1976 and hence the name.

Etiopathogenesis : This disease is epidemic occur in summer season due to

i. Spread of organism through contaminated water or air conditioning cooling towers.

ii. Immunosuppressed person ( corticosteroid therapy, old age)

iii. Cigarette smoking

MORPHOLOGICAL FEATURES :

Grossly : 

i. Consolidation of the entire lung.

ii. Pleural effusion is frequently present.

Histologically : 

i. Intra-alveolar exudate, initially of neutrophils later composed mainly macrophages.

ii. Alveolar septa shows  foci of hyperplasia of the lining epithelium and thrombosis of vessels in the septa.

iii. Special stains shows organism in the macrophages.

Features	Lobar Pneumonia	Lobular Pneumonia	Interstitial Pneumonia
Definition	It is an acute bacterial infection of a part of lobe or entire lobe or even two lobes of one or both the lungs.	It is the infection of terminal bronchioles that extend into the surrounding alveoli resulting in patchy consolidation of lung.	It is characterized by patchy inflammatory changes generally confined to interstitial tissue without any alveolar exudates.
Etiology	Pneumococci, Staphylococcal pneumonia.	Staphylococci, Streptococci etc.	Respiratory Syncytial Virus (RSV), Mycoplasma pneumoniae.
Morphology	Stage of congestion (1-2 days), Red hepatisation  (2-4 days), Grey hepatisation (4-8 days), Resolution (8-9 days)	Patchy consolidation with central granularity, alveolar exudate, thickened septa.	Patchy to massive and widespread consolidation of one or both the lungs.
Clinical features	Shaking, Chills, Fever, Malaise, Chest pain, Dyspnoea, Tachycardia, Tachypnoea and Cyanosis.	Shaking, Chills, Fever, Malaise, Chest pain, Dyspnoea, Tachycardia, Tachypnoea and Cyanosis, Mottled patches lung in X-rays.	Initially – Fever, Headache, Muscles pain. Later – Dry, Hacking, Cough with retrosternal burning.
Complications	Organisation, Pleural effusion, Empyema, Lung abscess, Metastatic infection.	Organisation, Pleural effusion, Lung abscess, Empyema.	Interstitial fibrosis and permanent damage.

CLINICAL FEATURES : This disease starts with-

i. Malaise.

ii. Headache.

iii. Muscles aches.

iv. High grade fever.

v. Chills.

vi. Cough.

vii. Tachypnoea.

viii. Abdominal pain.

ix. Water diarrhoea.

x. Proteinuria.

xi. Mild hepatic dysfunction.

Source : Textbook of pathology ( Harsh Mohan ) 7th edition

Related Posts -

• Pneumonia
• Lobar Pneumonia.
• Lobular Pneumonia or Bronchopneumonia.
• Interstitial Pneumonia
• Legionella Pneumonia.
• How to failed lungs defense mechanism.
• Textbook of pathology (Harsh Mohan ) 7th edition.