MASA syndrome A syndrome named for its characteristics: mental retardation, aphasia, shuffling gait, and adducted thumbs. Features of the syndrome include mental retardation and aphasia (lack of speech); adducted (clasped) thumbs, absent extensor pollicis longus and/or brevis muscles to the thumb, shuffling gait, and leg spasticity; small body size; and lumbar lordosis (swayback). MASA is…
Martin-Bell syndrome See fragile X syndrome.
marsh fever See malaria.
marriage, cousin See consanguinity.
Maroteaux-Lamy syndrome A form of mucopolysaccharidosis with onset before age 3 that is characterized by an inability to metabolize dermatan sulfate. This leads to abnormal accumulation of dermatan sulfate, mostly in the peripheral tissues. The result is mild to severe changes in muscle, bone, skin, and other tissues, particularly the heart. Diagnosis is made through…
marker 1 See gene marker. 2 A blood marker or a tumor marker. See also blood marker; tumor marker.
mark, strawberry See hemangioma, capillary.
marijuana A common street and recreational drug that comes from the marijuana plant: the hemp plant cannabis sativa. The pharmacologically active ingredient in marijuana is tetra-hydro-cannabinol (THC). Marijuana is used to heighten perception, affect mood, and relax. Many people think marijuana is harmless, but it is not. Signs of marijuana use include red eyes, lethargy,…
Marfan syndrome An inherited disorder of connective tissue that is characterized by abnormalities of the eyes, skeleton, and cardiovascular system. Nearsightedness (myopia) is the most common eye feature in Marfan syndrome. Displacement of the lens from the center of the pupil occurs in more than half of patients. Patients with Marfan syndrome have an increased…
marasmus See cachexia.
maple syrup urine disease A hereditary disease that is due to deficiency of an enzyme involved in amino acid metabolism, characterized by urine that smells like maple syrup. In maple syrup urine disease, the three branched-chain amino acids (leucine, isoleucine, and valine) cannot be metabolized (processed), and they build up in the blood, causing problems…
map-dot-fingerprint type corneal dystrophy See Cogan corneal dystrophy.