Dictionary

myxoma A benign tumor derived from connective tissue that has a gelatinous appearance. A myxoma is the most common type of primary tumor of the heart.

Na The chemical symbol for sodium. The symbol for sodium chloride (table salt) is NaCl. See also sodium.

nadir The lowest point. The nadir may refer, for example, to the lowest blood count after chemotherapy or the lowest concentration of a drug in the body.

nail 1 A piece of metal that is used to hold two or more pieces of bone together (for example, after a fracture). 2 The horny plate on the end of the finger (fingernail) or toe (toenail). Each nail has a body, lateral nail folds on its sides, a lunula (the little moon-shaped feature at…

nail care Care of the fingernails and toenails. Many nail problems are due to poor nail care. Recommendations for maintaining nail health include keeping nails clean and dry to keep bacteria and other infectious organisms from collecting under the nails, cutting nails straight across with only slight rounding at the tip, using a fine-textured file…

myalgia, epidemic See Bornholm disease.

myasthenia gravis An autoimmune neuromuscular disorder that is characterized by fatigue and exhaustion of muscles. Abbreviated MG. MG is caused by a mistaken immune response to the body’s own nicotinic acetylcholine receptors, which are found in junctions between muscles and the nervous system. The body produces antibodies that attack these receptors, preventing signals from reaching…

mycobacterium avium complex A serious opportunistic infection that is caused by two similar bacteria, Mycobacterium avium and Mycobacterium intercellulare, which are found in the soil and in dust particles. Abbreviated MAC. In persons with suppressed immune systems, such as people with AIDS, MAC can spread through the bloodstream to infect lymph nodes, bone marrow, the…

mycoplasma A large group of bacteria, with more than 100 types identified. Mycoplasma are very simple one-celled organisms without outer membranes. They penetrate and infect individual cells. Mycoplasma hominis and Mycoplasma pneumoniae are examples of mycoplasma bacteria that occur in humans.

mycoplasma hominis A common inhabitant of the vagina that can cause infections of the female and male genital tracts. Treatment involves use of antibiotics, including tetracycline and erythromycin.

mycoplasma pneumoniae A mycoplasma that can infect the upper respiratory tract and the lungs. Mycoplasma pneumoniae is a major cause of respiratory infection in children of school age and young adults. It is also a common cause of pneumonia in persons with HIV. Treatment involves use of antibiotics, including tetracycline and erythromycin.

mycosis fungoides A type of non-Hodgkin’s lymphoma that first appears on the skin. Also known as cutaneous T-cell lymphoma.