The genetic inheritance of palm print is polygenic and individual specific. It begins to develop in the 13th week of fetal life and is completed by the 19th week. Once formed, it remains constant throughout life and has a high degree of stability. Even in dizygotic children, although the overall structure appears to be identical, there are always some differences and the detailed patterns are not identical. The palm print can be divided into three main zones: the greater fissure, the lesser fissure and the interphalangeal zone. 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. In the second to fifth finger base each have a trigeminal point, in turn marked as a, b, c, d. In the lower part of the palm, under normal circumstances is at the bottom of the large and small intermarine, the base of the palm near the middle part, 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°. Trigeminal t′ occurs in 2% of normal individuals and 82% of congenital dysmorphic individuals, while trigeminal t″ occurs in 3% of normal individuals and 25% in trisomy 18, 81% in trisomy 13, and 80% in 5P- patients. Some abnormal palm prints have obvious correlation with genetic diseases and can be used for primary screening and auxiliary diagnosis of genetic diseases, especially chromosomal diseases. The way to judge the palm print is as follows: 1, through the fingerprint shape fingerprints according to the presence or absence and number of external trigeminal fingerprints are divided into three types: arch-shaped lines, skip-shaped lines and bucket-shaped lines (here the so-called trigeminal is a fingerprint in which three groups of crest lines of different directions converge in a "Y" or "human" shape). (the so-called "trigeminal" is a "Y" or "human" shaped fingerprint). Bow-shaped pattern: This is the simplest fingerprint pattern, which is characterized by a bow-shaped parallel texture, with the lines running from one side to the other, and the middle bulging like a bow, without trigeminal points. The lines start from one side, bend upward diagonally and then return to the original side, resembling a dustpan. The opening of the skip, that is, the side of the foot of the skip has a line in three directions, called the trigeminal point. According to the different orientation of the opening of the skip, it can be divided into the positive skip or the ruler's side skip and the opposite skip or the radial side skip. The opening of the positive skip faces the little finger on the home hand, and the opening of the fingerprint printed on the left hand faces to the right, while the opening printed on the right hand faces to the left. Diagonal fingerprints: These include ring-shaped, screw-shaped, sac-shaped, twisted, deviated, and deformed. The ring, screw and capsule shapes are commonly known as buckets. The twisted and deviated shapes are also known as double skips. All of these types have two trigeminal points, and they are included in the bucket pattern together for classification purposes. In normal people, each fingerprint pattern has a certain frequency of occurrence, and the majority of fingerprints on normal hands are of the orthogonal and diagonal types, while the arch-shaped and antigrade types are rare. However, there is an abnormality in the occurrence of fingerprints in patients with genetic diseases. For example, only 0-1% of the normal population has the opposite fingerprints of the 4th and 5th fingers, while the majority of patients with congenital stupidity have the opposite fingerprints. The total number of bowed fingerprints in both hands is greater than 7, which is only about 1% in the normal population, but up to 80% in patients with trisomy 18. The total number of fingerprint patterns in both hands is greater than 8, which is only 8% in the normal population, but reaches 32% in patients with 5P- (catcalling syndrome). The above cases are the skin pattern variations in patients with chromosomal disorders. Both monogenic and polygenic genetic disorders also have certain dermatoglyphic changes: increased ulnar skull in patients with spatial septal defect (a common congenital heart disease); increased radial skull in patients with atrial septal defect; increased bucket-shaped skull in patients with tetralogy of Fallot; increased ulnar skull and decreased bucket-shaped skull in patients with schizophrenia. 2. Judgment by palmar fold lines The palmar fold lines refer to the fold lines made by connecting 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 having a transverse hand is only 2% in the normal population, while it is 31% in congenital dysmorphism, 25% in trisomy 18, 62% in trisomy 13, and 35% in 50% of patients. 3.Total crest count The crest count refers to 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 syndrome, patients with reduced TRC values, also have another phenomenon: an increase in bowed lines. From the above, it is clear that genetic diseases tend to have dermatoglyphic abnormalities, and because dermatoglyphic analysis can be used for primary screening and auxiliary diagnosis of genetic diseases, especially chromosomal diseases. However, since abnormal skin lines can sometimes be seen in normal people, the diagnosis of genetic diseases can only be made with the application of other diagnostic indicators.