tic A repetitive movement that is difficult, if not impossible, to control. Tics can affect any group of muscles. The most common are facial tics, such as eye-blinking, nose-twitching, and grimacing. Tics that affect the muscles used to produce speech are known as vocal tics and can range from grunts or whistles to the repetition…
tic disorder A disorder that is characterized by the presence of tics. If both motor and vocal tics are present for more than 6 months, the diagnosis of Tourette’s syndrome may be made. Diagnosis is made via observation. Treatment can involve medications but is not usually recommended for minor tics that are not bothersome to…
tick bite A bite from a bloodsucking parasitic insect that punctures the skin with a sharp beak and burrows into the skin with its head. Tick bites can carry serious illness, including Rocky Mountain spotted fever, other forms of tick typhus, and Lyme disease. See also tick-borne disease.
tick-borne disease A disease that is carried by or caused by a tick. Examples of tick-borne diseases in the US include babesiosis (a malaria-like infection), ehrlichiosis, Lyme disease, relapsing fever (also called tick fever, most common in the western US), Rocky Mountain spotted fever, tick paralysis, and tularemia (rabbit fever). Anyone working in the outdoors,…
thrombinogen See prothrombin.
thrombocyte See platelet.
thrombocythemia An abnormally high number of platelets in the blood. Also known as thrombocytosis.
thrombocytopenia–absent radius syndrome See TAR syndrome.
thrombocytosis See thrombocythemia.
thromboembolism Formation in a blood vessel of a clot (thrombus) that breaks loose and is carried by the blood stream to plug another vessel. The clot may plug a vessel in the lungs (pulmonary embolism), brain (stroke), gastrointestinal tract, kidneys, or leg. Thromboembolism is a significant cause of morbidity (disease) and mortality (death), especially in…
thrombolytic agent See clot-dissolving medication.
thrombophilia The tendency to form thromboses (blood clots in arteries and veins).