Pneumonia

The term pneumonia usually refers to a syndrome caused by acute infection involving the lung parenchyma or interstitium usually due to bacteria and characterized by consolidation,both clinical and radiological,of a part of one or both lungs.The causative organisms can also be virus,parasites,mycobacteria and fungi.When noninfectious agents like chemicals and radiation cause pneumonia,the term pneumonia is used.
Classification:
1. Community-acquired pneumonia (CAP).
2. Hospital acquired (nosocomial) pneumonia.
3. Aspiration pneumonia.
4. Pneumonia in the immunocompromised bost including AIDS.
5. Recurrent pneumonia.
Causes:
`1. Bacteria -- Streptococcus pneumoniae,Mycoplasma pneumonia, Chlamydia pneumoniae,H. influenzae, Branhamella catarrhalis. Also M. tuberculosis,anaerobes,Gram negative pathogens and Staph. Aureus.
2. Primary atypical -- (a) Viral -- Psittacosis-ornithosis group, respiratory syncitial virus, measles and influenza, cytomegalovirus,adenviruses, varicella,herpes zoster,lymphocytic choriomeningitis.(b) Rickettsial -- Coxiella burneti (Q fever). (c) Mycoplasmal -- mycoplasma pneumoniae,Stevens-Johnson syndrome.
3. Protozoal -- Entamoeba histolytica.
4. Yeast and fungi -- Actinomycosis,aspergillosis,nocardiosis,histoplasmosis.
5.Chemical pneumonia -- (a) Aspiration of vomit.(b) Dysphagic pneumonia -- pharyngeal diverticulum, achalasia cardia, hiatus hernia or oesophageal stricture.(c) Lipoid pneumonia -- Kerosene,paraffin,petroleum.(d) Toxic gases and smokes.
6.Radiation pneumonia.

Symptoms:Onset often sudden although sometimes it follows a minor respiratory infection of a few days duration.
1. General symptoms of infection -- Malaise,fever,chills and rigors,vomiting; in the elderly confusion and disorientation.
2. Pulmonary symptoms -- Dyspnoea,cough,and sputum which is often blood-stained or rusty and difficult to expectorate.
3. Pleural symptoms -- Pain aggravated by cough, deep breath or movement,usually localised to site of inflammation.