The Dermal Ridges as the Infallible Signature of Skin: An Overview.

Our skin is the largest organ and is composed of the dermis and epidermis. The skin surface has lines in the direction of elastic tension. The palmar and plantar skin lines are established before birth in the intrauterine development of the embryo. Dermatoglyphics is the study of epidermal lines on the palmar and plantar surface. It is a branch of biology, anthropology, genetics, and dermatology. Dermatoglyphics are closely associated with genetic factors. These attributes once formed in the womb remain unique and persist throughout the life of an individual unless the dermis is damaged. Digital and palmar dermatoglyphics are represented by fingerprint patterns, atd angle, a, b, c, d triradii, mail line index, etc. Sometimes either due to hereditary reasons, the pressure of intrauterine factors, or external environmental factors, chromosomal aberrations occur in the fetus. These aberrations are reflected in the form of increased angle of atd, variation in pattern frequency or ridge count between a-b triradii (ABRC), presence of unnatural flexion creases, and others in the fingerprints, palmprints, or footprints. These aberrations in dermatoglyphics are useful in studying the genetic abnormalities in ailments, personality disorders, and criminal tendencies. Copyright:

Introduction

Human skin is the covering or integument layer covering all body parts. It is the largest organ, performing various functions. Human skin exhibits topographical differences. The thickness also varies from area to area. The skin on the face, eyes, chest, abdomen, and soles of the feet varies. Similarly, skin on the palms and plantar surface is different from other areas. Palmar and plantar surfaces have rugged lines, which show elevations and depressions, which serve as friction lines. These friction lines are formed when the fetus is developing and is in its third month. The whole process of friction line forming is completed by the sixth month of gestation. The scientific study of elevations (ridges) and depressions (furrows) is called dermatoglyphics. The ridge patterns on the skin are permanent and unique and stay so, from cradle to grave, unless the dermis is damaged.[1]

Researchers studied digital and palmar dermatoglyphics and found the genetic link to many medical disorders. They have been studying dermatoglyphics to gain an advantage in their predictive nature. Many medical disorders of genetic or nongenetic nature, dental ailments, and many others have been studied. Besides, dermatoglyphics has been found suitable to study the vocation or talent of an individual. The tendency to commit a crime is also genetically controlled as it has been found that brain cells and dermatoglyphics are controlled by the same set of cells that formulate brain processes, and dermatoglyphics never change as they are formed in the intrauterine life of a fetus.

Abbreviations

ATD: the angle between a-t-d triradii, ABRC: ridge count between a-b triradii, RH; Right hand, LH: Left hand, CR: criminal, C: control.

Digital dermatoglyphics

a. Fingerprint patterns

A fingerprint is an impression on a surface, left by friction ridges by a person's fingertip. The ridges and furrows form a design, which is called a pattern. The most important patterns are arch, loop, and whorl. Figure 1 exhibits common digital patterns.[2]

Figure 1

Common fingerprints patterns

Arches: In this pattern, we observe continuously raised ridges from one side of the finger to the other. Sometimes there is a sharper tent-like ridge structure in the center, and it is called a tented arch. Arches make up 5%–10% of the total population.

Loops: In this pattern, the ridges turn backward or recurve but not fully. There are two types of loops depending on the direction of the exit of loops: towards radial bone or ulnar bone. Accordingly, they are called radial and ulnar loops. They make up 60%–70% of the total population.

Whorl: Circular, spiral, or elliptical formations of ridges are found in this kind of pattern. Concentric circles are in a succession of rings, spiral whorls make a spiral around the core and turn clockwise or anticlockwise. Complex patterns are also included in whorls. Twinned loops, lateral pocket whorls, central pocket whorls, accidental whorls are all part of it. They make up 25%–30% of the total population.

b. Other landmarks:

Core: The innermost area of the pattern is called a core. It is the innermost area of the pattern. It is a fixed point for the pattern. It is of a different shape. For a loop, the central rod becomes the core, for a whorl, the core can appear as a dot or the starting of a spiral.

Delta/triradius: It is the outermost area of the loop. It is formed by the confluence of three ridges, which appear at an angle of 120° with each other.

Type lines: The lines originate from the delta and cover the pattern area.

Ridge counts: The number of ridges between core and delta is counted for each pattern. And all are added up to obtain total finger ridge count (TFRC). AFRC is also calculated for obtaining absolute count.

c. Pattern Type Indices: These are obtained by calculating the frequency distribution of various finger patterns. They are the Furuhata Index, Dankmeijer Index, and Pattern Intensity Index.[

where n = total number of samples

Palmar dermatoglyphics

The palm is divided into three areas: hypothenar, thenar, and interdigital area. Flexion creases, triraidii, and different types of patterns dominate the palmar surface. Thenar is shown by flexion radial longitudinal crease/thenar creases (lifeline). Distal transverse crease or line of heart and proximal transverse crease or line of head is prominent in the triradiate area. Below each finger, in the tridigital area, exists a triradius. Starting from index to little finger, they are labeled as “a, b, c, d.” In the axial area, near the base of the palm, exists another triradius called axial “t”.[3] Figure 2 exhibits the following palmar parameters:

Figure 2

A Palm depicting various regions and ATD angle, a-b ridge count, palmar lines

ATD Angle: ATD angle is formed by lines drawn from the digital “a” triradius to axial “t” triradius and from there to “d” triradius in the ID area. The angle so formed is measured at T using geometric instruments. The higher the position of “t,” the larger would be the angle.[4]

ABRC: Ridge count is obtained by counting the number of the ridges between the triradii “a & b.” An imaginary straight line is drawn connecting a-b and then, the ridges are counted.

Palmar flexion creases: The important flexion creases are distal transverse crease (heartline), proximal transverse (headline), and radial longitudinal crease (lifeline). These are further classified into single radial base crease (SRBC), double radial base crease (DRBC); and triple radial base crease (TRBC).

Palmar patterns: Varieties of patterns are found in palms. Loops occur as a downward loop, right loop, left loop, upward loop. Hypothenar/thenar areas are most frequented by whorls, twinned loops, elongated whorl, and arches.

Mainline creases: The main lines are A, B, C, D, and T. These originate from the digital triradii “a, b, c, d,” and line T from the axial triradius “t.” The mainline formula is formulated by tracing the main lines and is recorded in the order of D, C, B, A, and T.[5]

Use of Dermatoglyphics

In the detection of medical disorders

A. Genetic disorders:

Klinefelter's syndrome: The patients showed high frequencies of arches on fingertips, interdigital loops in the third right, right hypothenar patterns, and line C terminations in the right hand. It was also found that the mean a-b ridge count and mean value of Ltd angle of Klinefelter's syndrome patients were significantly different than that of the controls.[6]

Trisomy: In trisomy 8, a low TFRC and distally placed axial triradius were found along with high palmar and plantar pattern intensity. Loops with accessory triradius in an interdigital area in the thenar and hypothenar were found. Simian creases, bilateral arches on the great toes, and hallucal whorl were also observed. Whereas in trisomy 9, more whorls on digital area, raised total finger ridge count, and others as simian creases, and dissociation of palmar dermal ridges were seen. In trisomy18, increased frequency of radial loops on the thumb tips with a paucity of whorls on the fingertips was observed.[7]

Turner: It was observed that the patients had elevated total ridge count, a-b ridge count >105, and atd angle >120. Bilateral hypothenar patterns along with the longitudinal alignment of the main lines and transverse creases were also seen.[8]

Schizophrenia: It was observed that the male schizophrenic patients showed higher TFRC of each hand, whereas female schizophrenic patients had lower ridge count than their counterparts in control groups. TABRC was found to decrease in patients, and whorl patterns were more prominent, whereas controls had more frequency of loops.[910]

Down: It was observed that patients had mostly ulnar loop patterns in their fingertips. Abnormal dermatoglyphic features were found as the presence of simian crease, Sydney line, wide atd angle, and patterns in the hypothenar, interdigital areas, and subclassifications of the C-line terminations in the patient than control subjects.[11]

B. Non-genetic

Epilepsy: These patients had a higher mainline index on the right palm, higher occurrence of loops, and nil presence of vestiges, and lower counts of a-b triradii on both left and right palms.[1213]

Heart diseases: Wider ATD angle, increased hypothenar patterns, increased patterns in III interdigital area in males, higher values of total and absolute ridge counts.[141516]

Bronchial Asthma: Higher frequency of whorls was observed, higher values of a-b ridge count and higher TFRC were found in epileptic cases than controls.[171819]

Leprosy: In paucibacillary leprosy patients, an increase in the whorls and decrease in the loops were found, whereas in multibacillary leprosy patients, an increase in the loops and the decrease in whorls were observed. An increase in the double radial base crease was found in patients.[2021]

TB, Diabetes, Hyper tension:

Mean AFRC and TFRC in tuberculosis was higher, whereas patients with diabetes mellitus type II and hypertension showed a decrease in mean total finger ridge count. Mean “atd” angle in tuberculosis patients, diabetes mellitus type II, and hypertension was lesser than that of controls.[22]

Sydney crease and simian crease were found to be rare, and whorls were predominantly seen in TB patients, and diabetes mellitus type II and hypertension patients showed an increase in the number of arches and loops as compared to controls.

Cancer: It could be genetic as well as random. It was observed that in breast cancer patients, an increase in arch pattern and lower values of TFRC were observed. In oral squamous cell carcinoma, arches and loops were more frequent on fingertips in cases than in the controls, and loops were more in the interdigital areas in cases than in control. In carcinoma of cervix patients, a significantly increased frequency of whorls, TFRC, AFRC, and atd angle in both hands was observed along with the decreased frequency of ulnar loops and t-d ridge count in both hands.[232425]

C. Dental disorders:

Cleft lip and palate (CL/P): The patients exhibited six times thenar eminence, wider “atd” angle in palms along with more arches, double loops and ulnar loops, and low mean total ridge count in digits than in controls.[26]

Dental caries: Patients had more whorls on the fingertips, whereas caries-free students had more ulnar loops on the fingertips

Periodontal diseases: On all fingers, a decreased frequency of double loops followed by increased radial loops on the right second digits was seen along with an increased frequency of the tri-radii in the palms of the patients.

Potentially malignant disorders and oral carcinomas:

In the study of oral submucous fibrosis (OSMF), increased composite whorl pattern on left thumb, left little finger, decreased incidence of the radial loop on the left index followed by increased simple whorl pattern on the right thumb were observed.

In the study of oral squamous cell carcinoma, arches and loops were more frequent, and an increase in loops in the interdigital areas in cases was seen.

Dental malocclusion: In class II malocclusion patients, increased frequency of arches and ulnar loops, and fewer whorls were seen and in Class III, there was an increase of arches and radial loops with fewer ulnar loops.

Bruxism: These patients demonstrated an increase in the frequency of whorls, interdigital loops, and axial t tri-radii, termination of the mainline A in sector 5.

D. Skin disorders:

Psoriasis: Significant increase in the loops in males but not much change in atd angle and mean ABRC.[27]

Vitiligo: Increased incidence of loops on the fifth digit but no change in A-B ridge count. Mean atd angle decreased in females.

Alopecia areata: Increased incidence of loops in both sexes but no significant difference in atd angle and ABRC.

Hypohidrotic Ectodermal Dysplasia: Increased atd angle is observed.

In the detection of vocation/talent

Ulnar loop pattern was prevalent in all categories of students (Right hand: good 72%, average 58%, weak 40%, Left hand: good 72%, average 50%, weak 51%), and the higher symmetrical arrangement was observed in both hands (right and left hands) among the good students; however, no incidence of the arch pattern was recorded among the good set of students. More than two different sets of patterns were observed to be distributed in each hand among the weak category of students, and also asymmetrical arrangements were significant.[28]

In the identification of personality

There exists a linear relationship between children's boldness and the terminating end of the main palmar line D on the left hand.[29] Individuals having an arch pattern in their digits are likely to be introverts and cautious by nature, whereas people with tented arch are found to be highly unpredictable, sometimes shy, and sometimes outgoing.

In the detection of criminal tendencies

In the study done by Agarwal,[30] it was found that a higher frequency of whorls and arches and a lesser frequency of loops were found in the right hand of the control group as compared to prisoners. Welch[31] found that the criminal groups exhibited less ridge count and higher arch pattern frequency than the control group. Bali and Chaube[32] found that single radial base creases were more and double radial base creases were less in number in criminals than in the control group.

Conclusion

Dermatoglyphics has been widely used in understanding basic questions regarding skin morphology, evolution, anthropology, clinical medicine, and genetics besides being widely used for establishing identity. The development of dermal ridges starts along with the development of the brain, mammary glands, etc., and any chromosomal abnormality instruction received during gestation is reflected as distortion in the alignment of dermal ridges.

Dermatoglyphics is a simple, economical, anatomical, quicker, and noninvasive tool and may be used as a preventive and interceptive method not only in the detection of various medical disorders but also serves as a mirror to find one's potential and talent. It is a noninvasive tool to predict children who are at risk of becoming criminals. From the above discussion, it can be concluded that dermatoglyphics has an edge, in that it is fully formed at birth and are unique and permanent and remain unchanged for life, and is suitable as the best predictive tool.

Ethics approval and consent to participate

Ethical approval was not required, and consent was obtained from all the participants to use fingerprints data.

Participant consent

Written consent was obtained.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.