LAUSR

Heparin-induced thrombocytopenia, or HIT, occurs in some patients who have been taking the anticoagulant (blood thinner) heparin. Less commonly, drugs related to heparin called low-molecular-weight heparins (LMWHs) can cause HIT. Heparin and LMWH are used to treat clotting disorders, to prevent blood clots in certain heart conditions, and to prevent blood clots in patients who have undergone surgery or are hospitalized. Thrombocytopenia is the medical term for low platelets, which are blood cell fragments that help with clotting the blood in response to injury. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. The platelet count is low if it is less than 150,000. Platelets are measured on a routine blood test called a ‘CBC’ or complete blood count. Antibodies are blood proteins the body makes against substances it recognizes as foreign to help eliminate them. For example, people who catch the flu make antibodies that help fight the flu virus. In a similar way, vaccines trigger the body to make antibodies against infectious diseases like hepatitis or measles. Sometimes, though, the body makes antibodies to medications or, in the case of autoimmune diseases like rheumatoid arthritis and lupus, to parts of the body. HIT occurs when heparin or LMWH cause an immune reaction that creates antibodies that attach to platelets and heparin at the same time, causing platelets to stick together and be abnormally active, despite their low level in the bloodstream. When this occurs, the affected person is at high risk for developing blood clots in any blood vessel in the body.