Palmar pattern inheritance is polygenic and individual specific. It begins to develop in the 13th week of fetal life and completes in the 19th week, and once formed, it remains unchanged throughout life with a high degree of stability. Even in the case of identical twins, although the overall structure appears to be identical, there are always some differences and the detailed patterns are not exactly the same. Judging by the shape of fingerprints: Fingerprints are divided into three types according to the presence or absence and number of trigonometry at the outer end of the finger: bow-shaped lines, mini-shaped lines, and bucket-shaped lines (the so-called trigonometry is the fingerprints in which three sets of crests with different directions are converged in one place in the form of a “Y” or a “herringbone” shape). Bow-shaped pattern: This is the simplest fingerprint pattern, which is characterized by all the parallel textures in the shape of a bow, with the lines going from one side to the other, and the middle part of the fingerprints rising up like a bow, with no trigeminal points. Mini-shaped pattern: Commonly known as the dustpan in China, the lines start from one side, bend diagonally upwards and then return to the original side, resembling a dustpan. At the opening of the winnowing fan, i.e., the side of the foot of the fan, there is a line that goes in three directions, which is called the trident point. According to the different directions of the opening of the winnowing-pin, it can be divided into the positive winnowing-pin, or the ruler-side winnowing-pin, and the negative winnowing-pin, or the radial winnowing-pin. The opening of the positive minutiae faces the little finger of the present hand; the opening of the prints made by the left hand faces the right side, and the opening of the prints made by the right hand faces the left side. Bucket pattern: Includes ring, screw, sac, stranded, partial, deformed and so on. Ring, conch and sac are commonly known as bucket. The twisted and deviated types are also known as double skips. These types have two trigeminal points, and they are included in the range of bucket-shaped patterns in the classification. There is a certain frequency of occurrence of each fingerprint pattern in normal people, and the fingerprints of normal people’s hands are mostly of the types of positive skip and bucket pattern, while the bow-shaped pattern and anti-skip are rare. However, the frequency of fingerprints in patients with genetic diseases is abnormal. For example, in normal people, the 4th and 5th fingerprints are only 0-1%, while in patients with congenital stupidity, the majority of fingerprints are anti-skippers. The total number of fingerprints with a bow-shaped pattern in both hands is more than 7, which is only about 1% in the normal population, while it is as high as 80% in patients with trisomy 18. The total number of fingerprints in both hands with a bucket pattern greater than 8 is only about 8% in the normal population, while it reaches 32% in patients with 5P- (cat-call syndrome). The above cases are skin pattern changes in patients with chromosomal disorders. Both monogenic and polygenic genetic disorders also have some skin pattern changes: increased ulnar skip lines in patients with spatial septal defects (a common congenital heart disease); increased radial skip lines in patients with atrial septal defects; increased bucket lines in patients with Tetralogy of Fallot; and increased ulnar skip lines and decreased bucket lines in patients with schizophrenia.