DEFINITION Thrombocytosis is a disorder in which your body produces too many platelets (thrombocytes), which play an important role in blood clotting. The disorder is called reactive thrombocytosis or secondary thrombocythemia when it’s caused by an underlying condition, such as…
DEFINITION Thoracic outlet syndrome is a group of disorders that occur when the blood vessels or nerves in the space between your collarbone and your first rib (thoracic outlet) become compressed. This can cause pain in your shoulders and neck…
DEFINITION Tongue-tie (ankyloglossia) is a condition present at birth that restricts the tongue’s range of motion. With tongue-tie, an unusually short, thick or tight band of tissue (lingual frenulum) tethers the bottom of the tongue’s tip to the floor of…
DEFINITION Tonsil cancer is a type of cancer that begins in the cells of your tonsils. Your tonsils are two oval-shaped pads in the back of your mouth that are part of your body’s germ-fighting immune system. Tonsil cancer often…
DEFINITION Traumatic brain injury occurs when an external mechanical force causes brain dysfunction. Traumatic brain injury usually results from a violent blow or jolt to the head or body. An object penetrating the skull, such as a bullet or shattered…
DEFINITION Transverse myelitis is an inflammation of the spinal cord, which often targets insulating material covering nerve cell fibers (myelin). Transverse myelitis may result in injury across the spinal cord, affecting sensation below the injury. The disrupted transmission of nerve…
DEFINITION Transient global amnesia is a sudden, temporary episode of memory loss that can’t be attributed to a more common neurological condition, such as epilepsy or stroke. During an episode of transient global amnesia, your recall of recent events simply…
DEFINITION Trachoma (truh-KOH-muh) is a bacterial infection that affects your eyes. The bacterium that causes trachoma spreads through direct contact with the eyes, eyelids, and nose or throat secretions of infected people. Trachoma is very contagious and almost always affects…
DEFINITION Toxoplasmosis (tok-so-plaz-MOE-sis) is a disease that results from infection with the Toxoplasma gondii parasite, one of the world’s most common parasites. Toxoplasmosis may cause flu-like symptoms in some people, but most people affected never develop signs and symptoms. For…
DEFINITION Toxic shock syndrome is a rare, life-threatening complication of certain types of bacterial infections. Often toxic shock syndrome results from toxins produced by Staphylococcus aureus (staph) bacteria, but the condition may also be caused by toxins produced by group…
DEFINITION A tooth abscess is a pocket of pus that’s caused by a bacterial infection. The abscess can occur at different regions of the tooth for different reasons. A periapical (per-e-AP-ih-kul) abscess occurs at the tip of the root, whereas…
DEFINITION Tonsillitis is inflammation of the tonsils, two oval-shaped pads of tissue at the back of the throat — one tonsil on each side. Signs and symptoms of tonsillitis include swollen tonsils, sore throat, difficulty swallowing and tender lymph nodes…