Thrombocytopenia is the term used to describe a low platelet count. Platelets are the blood cells responsible for clotting off blood and preventing excessive bleeding. There are many reasons for a decreased platelet count, but in general, thrombocytopenia results from decreased platelet production; increased destruction; or increased sequestration, in which the spleen captures an excessive number of platelets.
Decreased Production
Since the platelets are formed in the bone marrow with the other blood cells, any process that affects the bone marrow can decrease the production of platelets. For example, certain cancers like leukemia can shut down the bone marrow, decreasing not only the number of platelets but of the other blood cells. 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. Other common causes of decreased production include chemotherapy drugs, which suppress the bone marrow in children receiving them as treatment for cancer.
Increased destruction
The most common cause for increased destruction of platelets in children is a condition called idiopathic thrombocytopenic purpura, or ITP. According to the Children's Hospital of Boston website, ITP results from the body mistakenly targeting platelets as foreign or invading cells. The body produces antibodies against platelets. These antibodies then signal the body's immune system that the platelets need to be destroyed. This results in a sudden decrease in the platelet count. Most children with ITP have a precedent viral illness that triggers the immune response against the platelets. Children with ITP often present with nosebleeds, easy bruising, and bleeding from the gums and other surfaces. Although this is a self-limited condition, children can be treated with steroids or other immune therapies to speed up their recovery.
Another common disease that causes thrombocytopenia in children is hemolytic-uremic syndrome, or HUS. This condition results after infection with a specific strain of E.coli, a common cause of diarrhea and food poisoning. Children with HUS suffer from thrombocytopenia and kidney failure.
Sequestration
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 the circulation, MayoClinic.com notes. This can happen if the spleen becomes enlarged by any number of conditions, for example with cirrhosis of the liver as a result of hepatitis infection.
