DEFINITION Sweet’s syndrome — also known as acute febrile neutrophilic dermatosis — is a rare skin condition marked by fever and painful skin lesions that appear mainly on your arms, neck, face and back. The exact cause of Sweet’s syndrome…
DEFINITION A thoracic aortic aneurysm is a weakened area in the upper part of the aorta. The aorta is the major blood vessel that feeds blood to the body. A thoracic aortic aneurysm may also be called thoracic aneurysm and…
DEFINITION Systemic mastocytosis (mas-to-sy-TOE-sis) is a rare disorder caused by a mutation that results in an excessive number of mast cells in your body. Mast cells normally help protect you from disease and aid in wound healing. But if you…
DEFINITION Systemic capillary leak syndrome is a rare disorder characterized by recurrent flares of massive leakage of plasma and other blood components from blood vessels into neighboring body cavities and muscles. This leads to swelling. The symptoms result from a…
DEFINITION Syringomyelia (sih-ring-go-my-E-lee-uh) is the development of a fluid-filled cyst (syrinx) within your spinal cord. Over time, the cyst may enlarge, damaging your spinal cord and causing pain, weakness and stiffness, among other symptoms. Syringomyelia has several possible causes, though…
DEFINITION Syphilis is a bacterial infection usually spread by sexual contact. The disease starts as a painless sore — typically on your genitals, rectum or mouth. Syphilis spreads from person to person via skin or mucous membrane contact with these…
DEFINITION Swollen lymph nodes usually occur as a result of exposure to bacteria or viruses. When swollen lymph nodes are caused by an infection, this is known as lymphadenitis (lim-fad-uh-NIE-tis). Rarely, swollen lymph nodes are caused by cancer. Your lymph…
DEFINITION A swollen knee occurs when excess fluid accumulates in or around your knee joint. Your doctor might refer to this condition as an effusion (ih-FYU-zhen) in your knee joint. Some people call this condition “water on the knee.” A…
DEFINITION Technically, the term “swine flu” refers to influenza in pigs. Occasionally, pigs transmit influenza viruses to people, mainly to hog farmers and veterinarians. Less often, someone infected passes the infection to others. The human respiratory infection caused by a…
DEFINITION Sweating and body odor are facts of life for most people. Heavy perspiration and body odor can happen when you exercise, when you’re too warm, or when you’re nervous, anxious or under stress. Your body has two main types…
DEFINITION A spermatocele (SPUR-muh-toe-seel) is an abnormal sac (cyst) that develops in the epididymis — the small, coiled tube located on the upper testicle that collects and transports sperm. Noncancerous and generally painless, a spermatocele usually is filled with milky…
DEFINITION Spina bifida is part of a group of birth defects called neural tube defects. The neural tube is the embryonic structure that eventually develops into the baby’s brain and spinal cord and the tissues that enclose them. Normally, the…