Neutropenia is when the body has abnormally low levels of certain white blood cells (called neutrophils), the body's main defense against infection.

More to Know

Many different medical conditions can cause neutropenia, including certain viral and bacterial infections, and cancer and cancer treatments. Both chemotherapy (powerful cancer-fighting drugs) and radiation (high-energy X-rays) work by killing the fastest-growing cells in the body — including healthy blood cells, like neutrophils.

Without the immune system defense provided by neutrophils, a person can be at high risk for infections. Kids and teens undergoing cancer treatment might have to stay home (and not attend school, work, or go to public places, etc.) while in a "neutropenic state."

Keep in Mind

Doctors can use a blood test called an absolute neutrophil count (ANC) to figure out how cautious someone needs to be about avoiding germs. Sometimes doctors use medications called growth factors to encourage the body to produce more neutrophils. But often it's safest just to remain home until the doctor says the neutropenia has passed.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.