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 risk for retinal detachment, glaucoma, and early cataracts. The skeleton shows bone overgrowth and loose joints. The arms and legs are unusually long, as are the fingers and toes. Due to overgrowth of the ribs, the sternum may be pushed in (pectus excavatum) or out (pectus carinatum). Scoliosis is common. Cardiovascular manifestations in Marfan syndrome include enlargement of the aorta at the level of the aortic valve, aortic aneurysm, prolapse of the mitral and tricuspid valves, and enlargement of the pulmonary artery. The major causes of disease and death in the syndrome are related to the heart and blood vessels. Marfan syndrome is inherited in an autosomal dominant manner and is caused by mutation in the FBN1 gene that encodes fibrillin 1. About 75 percent of people with Marfan syndrome have an affected parent, and 25 percent have a new gene mutation. Pregnancy can be dangerous for women with Marfan syndrome because the aorta can widen. Prevention of complications is key and includes exercise, blood pressure control, monitoring of the eyes, heart, and lungs, and physical therapy. Given good medical management, the life expectancy in Marfan syndrome now approximates that for the general population.
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, and uncoordinated body movements. The long-term effects may include decrease in motivation and […]
- Mark of Cain
The mark that God set upon Cain, the eldest son of Adam. According to the Book of Genesis in the Bible, God rejected Cain’s grain offering while accepting the animal offering of his brother Abel. Out of jealousy, Cain murdered his brother and was compelled by God to wander the earth as “a fugitive and […]
- Marker chromosome
An abnormal chromosome that is distinctive in appearance but not fully identified. A marker chromosome is not necessarily a marker for a specific disease or abnormality, but it can be distinguished under the microscope from all the normal human chromosomes. For example, the fragile X (FRAXA) chromosome was once called the marker X.
- Marker gene
A detectable genetic trait or segment of DNA that can be identified and tracked. A marker gene can serve as a flag for another gene, sometimes called the target gene. A marker gene must be on the same chromosome as the target gene and near enough to it so that the two genes (the marker […]
- Marker, blood
A sign of a disease or condition that can be isolated from a blood sample. For example, the monoclonal antibody D8/17 is a diagnostic sign of pediatric autoimmune disorders associated with streptococcus.