DEFINITION A lipoma is a slow-growing, fatty lump that’s most often situated between your skin and the underlying muscle layer. A lipoma, which feels doughy and usually isn’t tender, moves readily with slight finger pressure. Lipomas are usually detected in…
DEFINITION Lichen sclerosus (LIE-kun skluh-ROW-sus) is an uncommon condition that creates patchy, white skin that’s thinner than normal. Lichen sclerosus may affect skin on any part of your body, but most often involves skin of the vulva, foreskin of the…
DEFINITION Ductal carcinoma in situ (DCIS) is the presence of abnormal cells inside a milk duct in the breast. DCIS is considered the earliest form of breast cancer. DCIS is noninvasive, meaning it hasn’t spread out of the milk…
DEFINITION Drug addiction, also called substance use disorder, is a dependence on a legal or illegal drug or medication. Keep in mind that alcohol and nicotine are legal substances, but are also considered drugs. When you’re addicted,…
DEFINITION With leukoplakia (loo-koh-PLAY-key-uh), thickened, white patches form on your gums, the insides of your cheeks, the bottom of your mouth and, sometimes, your tongue. These patches can’t be scraped off. Doctors don’t know what causes leukoplakia but consider tobacco…
DEFINITION Legionnaires’ disease is a severe form of pneumonia — lung inflammation usually caused by infection. Legionnaires’ disease is caused by a bacterium known as legionella. You can’t catch Legionnaires’ disease from person-to-person contact. Instead, most people get Legionnaires’ disease…
DEFINITION In a female fetus, the uterus starts out as two small tubes. As the fetus develops, the tubes normally join to create one larger, hollow organ — the uterus. Sometimes, however, the tubes don’t join completely. Instead, each one…
DEFINITION Lichen nitidus (LIE-kun ni-TIE-dus) is a rare skin condition that usually appears as tiny, skin-colored, glistening bumps on the surface of your skin. Lichen nitidus results from abnormal inflammatory activity in skin cells, but the cause of inflammation is…
DEFINITION Lice are tiny, wingless, parasitic insects that feed on your blood. Lice are easily spread — especially by schoolchildren — through close personal contact and by sharing belongings. Several types of lice exist: Head lice. These lice…
DEFINITION Lewy body dementia, the second most common type of progressive dementia after Alzheimer’s disease, causes a progressive decline in mental abilities. It may also cause visual hallucinations, which generally take the form of objects, people or animals that aren’t…
DEFINITION Diffuse idiopathic skeletal hyperostosis (DISH) is calcification or a bony hardening of ligaments in areas where they attach to your spine. Also known as Forestier’s disease, diffuse idiopathic skeletal hyperostosis may cause no symptoms and require…
DEFINITION Klinefelter syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. Klinefelter syndrome is a common genetic condition affecting males. Klinefelter syndrome adversely affects testicular growth, and this can…