1.Concept Marfan syndrome, also known as congenital mesodermal dysplasia, Marchesani syndrome, spider’s finger, limb slenderness, is a dominant genetic disorder. It mainly manifests as peripheral connective tissue dystrophy, skeletal abnormalities, internal eye disease and cardiovascular abnormalities, and is a genetic disease with basic defects in connective tissue. 2, dominant genetic disease Just one allele abnormality in the gene can lead to autosomal dominant genetic disease. Autosomal dominant disorders in which there is vertical transmission. There are usually several rules: (1) one of the parents of the patient has the disease; (2) the average number of children born to a patient and a normal person have the disease and do not have the disease; (3) if one parent has the disease and he or she does not have the disease, his or her offspring will not have the disease; (4) men and women have an equal chance of having the disease; (5) the incidence of the disease in the children of the patient is 50%. (6) Genealogy is based on phenotypes (observable characteristics). The genotype can also be determined and recorded using molecular biology. In other words, if neither parent has the disorder, don’t worry about your child having Marfan syndrome. Take the earlobe example as follows: Autosomal dominant inheritance refers to the inheritance of traits controlled by dominant genes on the autosomes. Since having earlobes is dominant to having no earlobes, it is controlled by a pair of genes (A, a), then individuals with genotypes AA and Aa both have earlobes. If a person with earlobes marries a person without earlobes, if the person with earlobes is heterozygous (Aa), half of the children will have no earlobes. 3. Diagnostic criteria Special skeletal changes, i.e. elongated tubular bones, especially finger and metacarpal bones. The bone cortex becomes thin and slender, showing spider finger-like changes. (1) Thin and tall body with slender limbs, especially forearms and thighs ① height > 180cm; ② finger spacing > height (with both hands flat, the distance between the two middle fingers – height > 7.6cm has diagnostic value); ③ lower body (from pubic symphysis to sole) > upper body (from the top of the head to the pubic symphysis) with a ratio > 0.92 (normal people ≤ 0.92). (2) Spider finger/toe like changes ① The fingers (toes) are particularly long, showing typical spider-like changes, with the ratio of hand to height >11% and the ratio of foot to height >15%; (finger length: the hand length is the straight line distance from the midpoint of the lateral palmar line connecting the radial tuberosity point and the ulnar tuberosity point (this point corresponds approximately to the midpoint of the wrist joint skin flexion line) to the tip of the middle finger. (Foot length: the maximum linear distance between the point of the heel (pte) and the tip of the longest toe (ap) (first or second toe), parallel to the line from the point of the heel (pte) to the tip of the second toe (ap Ⅱ)) ② Thumb sign: the thumb is tucked in, the remaining four fingers make a fist, the tip of the thumb exceeds the lower edge of the palm, about half of the patients have this sign; ③ Wrist sign: holding the radial styloid process with one hand in the other hand The thumb and little finger can be in contact without pressure; ④ The metacarpal index is increased, the metacarpal index is <8 in normal people and >8.4 in patients with this disease (8.4-10.5), and the metacarpal index is measured on X-ray, which is the ratio of the length and width of the 2nd to 5th metacarpal of the right hand. Normal is 5.5 to 8.0; 8.1 to 8.3 suggests (possible) diagnosis, ≥8.4 confirms the diagnosis of the disease. (5) Other finger (toe) abnormalities: pestle fingers, webbed fingers (toes), thin palms, flat feet may be present. (3) cranial lesions ① long head, narrow face, convex palate; ② cranial index > 75.9; (cranial index is equal to the maximum transverse diameter of the head / maximum anterior and posterior diameter of the head × 100) ③ the distance between the eyes is too wide or too narrow, long lower jaw; ④ uneven teeth, lack of wisdom teeth, etc.; ⑤ both ears forward or drooping, the ear wheel is thin, shaped like the elderly. (4) Thoracic and spinal deformities ①Cocky chest, flat chest, funnel chest; ②Hunchback, lateral spinal protrusion or spina bifida. (3) Congenital cardiovascular abnormalities. (5) Eye symptoms (1) Bilateral lens dislocation or subluxation, or total dislocation with high myopia. (2) Retinal detachment, iris tremor, cataract (occurring in the late stage of the disease), strabismus, pupil narrowing, secondary glaucoma, etc. (4) Family history. The diagnosis is confirmed by three of the above four clinical criteria, and incomplete Mafang syndrome can be diagnosed by the presence of only two changes in the first three items. 4. Prognosis One-third of patients with Mafang syndrome die before the age of 32, and two-thirds die around the age of 50. The main cause of death is overwhelmingly a cardiovascular lesion. The most common are heart failure or myocardial ischemia due to aortic aneurysm rupture, pericardial compression or incomplete aortic valve closure and mitral valve prolapse, and severe arrhythmias.