Pneumonia

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Pneumonia

Introduction

Signs and symptoms

Diagnostic tests

Treatment of pneumonia

Conditions predisposing to pneumonia

[edit] Pneumonia

Introduction:

This is an infection of the lung tissue and can either affect an entire lobe (lobar pneumonia)of the lung or a segment of it (segmental pneumonia). The clinician cannot make this distinction, but on lung x-rays these distinctions can be made.

In the US about 2 million people come down with pneumonia each year and about 50,000 die from it, the 6th most common cause of all deaths (Ref. 9, p. 601). The most common cause of pneumonia in the adult are bacteria, whereas in children and infants viral infections are more common. Pneumonia often develops as a secondary step following a viral infection that leaves inflammation in an area of the lung where pneumonia can develop subsequently or else when a "foreign body is aspirated". The medical term "foreign body aspiration" pertains to any of the following situations: it can be when a child inhales a small particle, like a peanut or small part from a toy. In adults it can be a reflux problem where stomach acid or food particles get aspirated during sleep or when under the influence of drugs or alcohol. In the very old nursing home residents who may lose their protecting cough reflex this makes them also more vulnerable to develop aspiration pneumonia. This link explains that often bronchoscopy is needed in these cases.

Common bacteria causing pneumonia:
Streptococcus pneumoniae	Chlamydia pneumoniae
Haemophilus influenzae	Chlamydia psittaci
Staphylococcus aureus	Chlamydia trachomatis
Moraxella catarrhalis	Legionella pneumophila
Common viruses causing pneumonia:
respiratory syncytial virus (RSV)	parainfluenza virus
influenza A	influenza B
Rarer causes of pneumonia:
Mycobacterium tuberculosis	Coccidioides immitis
Histoplasma capsulatum	Blastomyces dermatitidis
Cryptococcus neoformans	Pneumocystis carinii
Aspergillus fumigatus	Coxiella burnetii (Q-fever)
SARS coronavirus	bird flu (type A, H5N1 strain)

This table lists common causes of pneumonia.

However, there are certain high risk situations where more rare forms of pneumonia occur. For instance in AIDS, where the immune system is weakened from the AIDS virus, interstitial pneumonia with Pneumocystis carinii is very common.

This pathogen, which has been considered to be a protozoan parasite, has recently been shown to have DNA sequences of a fungus type. X-rays show typical interstitial infiltrates on both lungs. Bronchoscopy is indicated to obtain samples from the infected areas for culture and microscopic identification. Other pathogens in tghe fungal and viral category are also common as secondary infections in AIDS.

There are other situations where pneumonia is common, for instance in patients who had received transplants (heart, kidney, liver etc.) as the immune system is weakened from the ongoing immunosuppression to prevent organ rejection.

Another high risk situation is in a person who is undergoing chemotherapy for cancer where the immune system is being weakened as a side-effect of the chemotherapy. This allows any of the pathogens to invade the lung tissue.

Other high risk scenarios are patients who had burn injuries, chronically ill patients with other conditions who are in Intensive Care Units or older people who are in nursing homes, chronic care homes etc.

Home page

Respiratory Infection

Infections overview

Pneumonia

References:

1. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 161.

2. TC Dixon et al. N Engl J Med 1999 Sep 9;341(11):815-826.

3. F Charatan BMJ 2000 Oct 21;321(7267):980.

4. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 43.

5. JR Zunt and CM Marra Neurol Clinics Vol.17, No.4,1999: 675-689.

6. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 162.

7. LE Chapman : Antivir Ther 1999; 4(4): 211-19.