Thrombocytopenia is the term used to describe a low platelet count. Platelets are blood cells responsible for clotting blood and preventing excessive bleeding. There are many reasons for a decreased platelet count in children, but in general, thrombocytopenia results from decreased platelet production, increased destruction of platelets or increased sequestration, occurring when the spleen captures an excessive number of platelets. See your pediatrician if your child has symptoms of this condition.
Platelets are formed in the bone marrow with other blood cells, and any process that affects the bone marrow can decrease the production of platelets. For example, certain cancers such as leukemia can shut down the bone marrow, decreasing not only the number of platelets but the number of the other blood cells as well. Viruses such as mumps, Epstein-Barr -- which causes infectious mononucleosis, and parvovirus can also decrease the production of platelets, mainly by replicating within the cellular precursor of platelets. Chemotherapy drugs, which suppress the bone marrow, also cause decreased platelet levels in children.
The most common cause of increased destruction of platelets in children is a condition called idiopathic thrombocytopenic purpura, or ITP. This condition occurs when the body mistakenly targets platelets as foreign or invading cells. The body produces antibodies against platelets. These antibodies then signal the body's immune system to destroy the platelets. This causes a sudden decrease in the platelet count. Most children with ITP have a precedent viral illness that triggers the abnormal immune response. Children with ITP often present with nosebleeds, easy bruising, and bleeding from the gums and other surfaces.
Another common disease that causes thrombocytopenia in children is hemolytic-uremic syndrome, or HUS. This condition occurs after infection from a specific strain of E.coli, a common cause of diarrhea and food poisoning. Children with HUS suffer from thrombocytopenia and kidney failure.
The spleen is part of the body's immune system, and in certain conditions it can capture an excessive number of platelets, decreasing their numbers in circulation. This can happen if the spleen becomes enlarged by any number of conditions, including cirrhosis of the liver as a result of hepatitis infection.