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What is leprosy? Leprosy, also known as Hansen’s disease (HD), is a chronic infectious disease caused by a Mycobacterium (Mycobacterium leprae) affecting especially the skin and marginal nerves. It is characterized by the formation of nodules or macules that enlarge and spread with loss of sensation and eventually paralysis, wasting …

Definition Lassa fever is an acute viral hemorrhagic illness caused by the lassa virus, a member of the arenavirus family of viruses. It is transmitted to humans from contacts with food or household items contaminated with rodent excreta. The disease is endemic in the rodent population in parts of west …

Definition Listeriosis is an infection caused by a gram stain-positive motile bacterium named Listeria monocytogenes. The foodborne illness produces fever, muscle aches, and, in many people, diarrhea. Severe infections can cause headaches, meningitis, convulsions, and death. Most healthy people exposed to the bacteria have minor or no symptoms, but a …

Definition Lactose intolerance is a common digestive problem where the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products. Lactose intolerance develops when the body does not specifically make an enzyme called lactase. Lactase is needed to break down lactose the sugar …

Definition Leukemia is a malignancy (cancer) of blood cells. In leukemia, abnormal blood cells are produced in the bone marrow. Usually, it involves the production of abnormal white blood cells the cells responsible for fighting infection. However, the abnormal cells in leukemia do not function in the same way as …

Definition Laryngitis is inflammation in and around the mucus membranes of the larynx or voice box. The irritated larynx becomes swollen and painful, leading to a sore throat, hoarse voice and even a complete loss of voice. Most cases of laryngitis are caused by an infection. Epidemiology Accurate figures regarding …

Definition Primary liver cancer is a condition that happens when normal cells in the liver become abnormal in appearance and behavior. The cancer cells can then become destructive to adjacent normal tissues, and can spread both to other areas of the liver and to organs outside the liver. Malignant or …

Definition Lung cancer is a disease in which certain cells in the lungs become abnormal and multiply uncontrollably to form a tumor. Lung cancer may not cause signs or symptoms in its early stages. Some people with this have chest pain, frequent coughing, and blood in the mucus, breathing problems, …