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Atypical pneumonia

Definition

Atypical pneumonia refers to pneumonia caused by certain bacteria, including Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae.

Pneumonia is a condition in which there is an infection of the lung.

Alternative Names

Walking pneumonia; Chlamydophila pneumoniae; Community-acquired pneumonia - atypical

Causes, incidence, and risk factors

Mycoplasma pneumonia is a type of atypical pneumonia. It is caused by the bacteria M. pneumoniae. It typically affects people younger than age 40. For more information on this type of pneumonia, see: Mycoplasma pneumonia

Pneumonia due to chlamydia-related bacteria occurs year round and accounts for 5 - 15% of all pneumonias. It is usually mild.

Pneumonia due to Legionella is seen more often in middle-aged and older adults, smokers, and those with chronic illnesses or a weak immune system.

See also: Legionnaire's disease

Symptoms

Pneumonia due to mycoplasma and chlamydophila bacteria is usually mild.

• Pneumonia due to Legionella pneumophila gets worse during the first 4 - 6 days, and then improves over 4 - 5 days.
• Even though symptoms will improve, it may take a while for them to go away completely.

The most common symptoms of pneumonia are:

• Chills
• Cough (with Legionella pneumonia, you may cough up bloody mucus)
• Fever, which may be mild or high
• Shortness of breath (may only occur when you climb stairs)

Other symptoms include:

• Chest pain that gets worse when you breathe deeply or cough
• Confusion, especially in older people or those with Legionella pneumonia
• Headache
• Loss of appetite, low energy, and fatigue
• Muscle aches and joint stiffness
• Sweating and clammy skin

Less common symptoms include:

• Diarrhea (especially with Legionella pneumonia)
• Ear pain (with mycoplasma pneumonia)
• Eye pain or soreness (with mycoplasma pneumonia)
• Neck lump (with mycoplasma pneumonia)
• Rash (with mycoplasma pneumonia)
• Sore throat (with mycoplasma pneumonia)

Signs and tests

Persons with suspected pneumonia should have a complete medical evaluation. It may be hard for your health care provider to tell whether you have pneumonia or bronchitis, so you may need a chest x-ray. Depending on the severity of the illness, other tests may be done, including:

• Complete blood count (CBC)
• Blood cultures
• Blood tests to identify the bacteria
• Bronchoscopy (rarely needed)
• CT scan of the chest
• Open lung biopsy (only done in very serious illnesses when the diagnosis cannot be made from other sources)
• Sputum culture

Urine tests or a throat swab may also be done.

Treatment

Take these steps at home:

• Control your fever with aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen or naproxen), or acetaminophen. DO NOT give aspirin to children.
• Do not take cough medicines without first talking to your doctor. Cough medicines may make it harder for your body to cough up the extra sputum.
• Drink plenty of fluids to help loosen secretions and bring up phlegm.
• Get a lot of rest. Have someone else do household chores.

Antibiotics are used to treat atypical pneumonia.

• You may be able to take antibiotics by mouth at home.
• If you have severe atypical pneumonia, you will likely be admitted to a hospital, where you will be given antibiotics through a vein (intravenously), as well as oxygen.
• Antibiotics are used for 2 weeks or more

Antibiotics used to treat atypical pneumonia include:

• Azithromycin
• Clarithromycin
• Erythromycin
• Fluoroquinolones and their derivatives (such as levofloxacin)
• Tetracyclines (such as doxycycline)

Support Groups

Expectations (prognosis)

Most patients with pneumonia due to mycoplasma or chlamydophila do well with the right antibiotic therapy. P.Legionella can be severe, leading to problems such as kidney failure, diabetes, COPD, a weak immune system, and death.

Complications

• Brain and nervous system infections, such as meningitis, myelitis, and encephalitis
• Hemolytic anemia, a condition in which there are not enough red blood cells in the blood because the body is destroying them
• Severe lung damage

Calling your health care provider

Contact your health care provider if you develop fever, cough, or shortness of breath. There are numerous causes for these symptoms. The doctor will need to rule out pneumonia.

Prevention

Wash your hands often and have other people around you do the same.

If your immune system is weak, stay away from crowds. Ask visitors who have a cold to wear a mask.

Get a flu shot every year. Ask your doctor if you need a pneumonia vaccine.

References

Baum SG. Mycoplasma pneumoniae and atypical pneumonia. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 184.