The palm print can be divided into three main zones: the greater interphalangeal area, the lesser interphalangeal area and the interphalangeal area. The greater interphalangeal area is located below the thumb. The lesser interphalangeal area is located below the side of the little finger of the palm. At the base of the second to the fifth finger there is a trigeminal point, labeled a, b, c, d. At the bottom of the palm, normally at the bottom of the greater and lesser interphalangeal, near the base of the palm, there is a trigeminal point, called trigeminal t. From the t point to a and d line to get an angle, called atd angle. The atd angle of a normal person is generally expressed by “t”, and the average atd angle of a normal person in China is about 41°. However, some patients with genetic diseases have changes in the location of the trigeminal t site on the resident hand, which makes the atd angle abnormal. The abnormal atd angle is indicated by “t′” and “t″,” 46°< t′< 63°< t″. For example, the mean at′d angle in patients with congenital dysmorphism is approximately 70°. The presence of trigeminal point t′ is 2% in normal individuals, 82% in congenital dysmorphic individuals, and trigeminal point t″ is 3% in normal individuals, while it is 25% in trisomy 18, 81% in trisomy 13, and 80% in 5P- patients. The palm crease refers to the crease line that connects the skin with the deep fascia. In normal people, there are three major palmar folds: the large fissure fold, the proximal transverse fold and the distal transverse fold. The proximal transverse folds are connected to the transverse interfascicular folds on the radial side, while the distal transverse folds are separated. There is a type of palmar fold that is called the transverse hand, in which the distal and proximal folds are combined into a single fold that runs across the entire palm. The percentage of people with both hands with a transverse hand is only 2% in the normal population, compared to 31% in congenital dysmorphism, 25% in trisomy 18, 62% in trisomy 13, and 35% in 50% of patients. Total crest count The crest count is performed by drawing a straight line from the center of the skip or bucket crest to the center of the trigeminal point, and then counting the number of crests that the line passes through. The total number of crests (TRC) is obtained by adding the number of crests on the 10 fingers of the left and right hands. Since there are two trigeminal lines, two numbers are calculated separately, but only the larger number is counted when calculating the total. In patients with sex chromosome variants, the relationship between the TRC and the number of sex chromosomes is prominent: for each additional X chromosome, the TRC value decreases by 30; for an additional Y chromosome, it decreases by 12. For example, in Turner syndrome, the TRC value increases significantly (60-203), compared to 127 in normal women; in Klinefelter In Klinefelter syndrome, the TRC value is reduced and there is also another phenomenon: an increase in bowing lines.