Dr. Greene`s Answer:
Mycoplasmas are the smallest free-living creatures ever discovered. Dwarfed by amoebas, they are smaller even than bacteria (or perhaps than “other bacteria”–sometimes they are classified as the smallest bacteria). They are the original “morphers”–changing shape from long, thin filaments to little spheres to intricate branching patterns to bulbs to an endless variety of asymmetric shapes, like the latest science-fiction special effects. They grow and reproduce very slowly for such tiny organisms.
Almost 100 species of mycoplasmas have been identified and are plentiful everywhere in nature. Fifteen species are known to live in humans, most as normal and helpful intimate neighbors.
Many pediatricians still consider mycoplasmas an uncommon cause of disease, but that is largely because our tests have been inadequate. Infectious diseases are often identified by “culturing” them–taking a small sample of tissue or fluid and keeping it in an incubator for a while to see what grows. Mycoplasmas are very tiny, shape-shifting, slow-growing critters that don’t often show up on cultures.
But newer, more sensitive antibody tests prove mycoplasmas to be a common cause of infection. Over 40% of children have had a mycoplasma infection by their first birthday, more than 65% by age 5 years, and 97% by adulthood. Repeat infections, even severe repeat infections, are common.
In addition to pneumonia, mycoplasmas can cause a variety of other respiratory illnesses, including ear infections, sinus infections, bronchitis, croup, bronchiolitis, severe sore throats, infectious asthma, and even a version of the common cold. Most mycoplasma infections are not very severe but last for quite a long time.
Mycoplasma infections may cause more severe infections in children with weak immune systems (especially those with hypogammaglobulinemia), Down syndrome, sickle cell disease or trait, and some heart or lung conditions.
Last reviewed: February 12, 2009