Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs (alveoli)—associated with fever, chest symptoms, and a lack of air space (consolidation) on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes. Infectious agents include: bacteria, viruses, fungi, and parasites.
Typical symptoms include cough, chest pain, fever, and difficulty breathing. Diagnostic tools include x-rays and examination of the sputum. Vaccines to prevent certain types of pneumonia are available. Treatment depends on the underlying cause with presumed bacterial pneumonia being treated with antibiotics.
Although pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death", the advent of antibiotic therapy and vaccines in the 20th century have seen radical improvements in survival outcomes. Nevertheless, in the third world, and among the very old, the very young and the chronically ill, pneumonia remains a leading cause of death.
People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, confusion, and an increased respiratory rate. In the elderly, confusion may be the most prominent symptom. The typical symptoms in children under five are fever, cough, and fast or difficult breathing. Fever, however, is not very specific, as it occurs in many other common illnesses, and may be absent in those with severe disease or malnutrition. Additionally, a cough is frequently absent in children less than 2 months old. More severe symptoms may include: central cyanosis, decreased thirst, convulsions, persistent vomiting, or a decreased level of consciousness.
|Symptoms frequency in pneumonia|
|Shortness of breath|| |
|Chest pain|| |
Some causes of pneumonia are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by Legionella may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by Streptococcus pneumoniae is associated with rusty colored sputum, and pneumonia caused by Klebsiella may have bloody sputum often described as "currant jelly".
Physical examination may sometimes reveal low blood pressure, a high heart rate, or a low oxygen saturation. Examination of the chest may be normal, but may show decreased chest expansion on the affected side. Harsh breath sounds from the larger airways that are transmitted through the inflamed lung are termed bronchial breathing, and are heard on auscultation with a stethoscope. Rales (or crackles) may be heard over the affected area during inspiration. Percussion may be dulled over the affected lung, and increased, rather than decreased, vocal resonance distinguishes pneumonia from a pleural effusion. Struggling to breathe, confusion, and blue-tinged skin are signs of a medical emergency.
Pneumonia is primarily due to infections, with less common causes including irritants and the unknown. Although more than one hundred strains of micro organisms can cause pneumonia, only a few are responsible for most cases. The most common types of infectious are viruses and bacteria with it being less commonly due to fungi or parasites. Mixed infections with both viruses and bacterial may occur in up to 45% of infections in children and 15% of infections in adults. A causative agent is not isolated in approximately half of cases despite careful testing. The term pneumonia is sometimes more broadly applied to inflammation of the lung (for example caused by autoimmune disease, chemical burns or drug reactions), however this is more accurately referred to as pneumonitis.