Mycoplasma Pneumoniae Infections and Cold Agglutinin Disease

Emily Malcolm, PhD avatar

by Emily Malcolm, PhD |

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bacteria infections, secondary CAD

Cold agglutinin disease (CAD) is a rare autoimmune disease in which the immune system produces antibodies against the body’s own red blood cells. In cold temperatures, these antibodies bind tightly to these cells, causing them to clump together.

Secondary CAD — where the increase in cold agglutinin antibodies is due to an underlying condition — can be caused by an infection from bacteria such as Mycoplasma pneumoniae (M. pneumoniae).

What is M. pneumoniae?

M. pneumoniae is a type of bacterium that commonly causes mild upper respiratory infections such as chest colds, sometimes called “walking pneumonia.”

In rare cases, it can also lead to pneumonia, which may require hospitalization, as well as increase the antibodies that cause CAD.

How does a M. pneumoniae infection cause CAD?

Cold agglutinin antibodies are normally produced in very low amounts by the immune system in response to an infection. It is unknown why some infections such as M. pneumoniae can cause a big increase in cold agglutinin antibodies, leading to CAD.

How are M. pneumoniae infections treated?

M. pneumoniae infections are treated with antibiotics. In reported cases, the symptoms of CAD were eliminated following antibiotic treatment and after the pneumonia infection cleared.

How can M. pneumoniae infections be prevented?

Like many respiratory infections, M. pneumoniae is spread by coughing and sneezing. Having had these infections previously does not make you less susceptible to the infection, so protect yourself by taking the following measures:

  • Cover your mouth when you cough or sneeze.
  • Wash your hands frequently and thoroughly (at least for 20 seconds) with soap and water.
  • Avoid touching your eyes, nose, and face to prevent transmission of germs through your mucous membranes.


Last updated: Dec. 5, 2019


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