The genetics of palmar creases. A study in the inheritance of liability estimated from the incidence among relatives

Prevalence of the Different Types of Palmar Creases Among Medical and Dental Students in Addis Ababa, Ethiopia

Background

Studies have suggested that identification of aberrant palmar creases may give clues for an early and noninvasive method of diagnosis of certain disease conditions. Toward this purpose, awareness of the normal variants of palmar creases must be first recognized. Accordingly, this study aimed to investigate the patterns of palmar creases in healthy Ethiopian population among Medical and Dental Students in Addis Ababa.

Subjects and Methods

Right and left palm pictures from 318 (177 females and 141 males) participants were taken using a mobile camera, and evaluated qualitatively. Observations were analyzed by Fisher's exact test, and significance levels for comparisons were set at p<0.05.

Results

Aberrant creases were observed in 13.8% of the palms. Simian crease was the most common among the aberrant crease types, followed by Suwon and Sydney. Palmar creases with two and three points of origin were significantly more common, respectively, in males and the females. Minor variants as accessory to the radial longitudinal crease and middle longitudinal crease were also observed.

Conclusion

This study suggests that aberrant crease types at the observed frequencies may not be indicative of known disease conditions as they occurred in apparently healthy Ethiopians. However, the results of this study, besides revealing the patterns of palmar creases among Ethiopians, could give a baseline for studies aimed at diagnosis of disease conditions based on palmar crease configurations. Further qualitative and quantitative studies of palmar creases in wider populations with various conditions, including ethno-geographic factors, are recommended.

The simian crease: Relationship to various genetic disorders

The creases of the palm have been of interest for clinicians, anthropologists, and palmists for hundreds of years, but the variations in them have only been studied during the past 50 years. The simian crease, aptly named for its resemblance to the palmar creases of nonhuman simian primates, has received recognition clinically and anthropologically owing to its abnormal appearance and confounding cytogenetic etiology. Given the rarity of these palmar creases but also their usefulness in diagnosing congenital disorders, discussion of cases of those disorders could provide clinicians with further helpful diagnostic knowledge. This review of the literature focuses on the history, embryology, genetic and hereditary origins, and clinical significance of simian creases for the benefit of the diagnosing clinician. Clin. Anat. 32:1042-1047, 2019. © 2019 Wiley Periodicals, Inc.

Minor physical anomalies in adults with autism spectrum disorder and healthy controls

Minor Physical Anomalies (MPAs) are subtle abnormalities of the head, face, and limbs, without significant cosmetic or functional impact to the individual. They are assumed to represent external markers of developmental deviations during foetal life. MPAs have been suggested to indicate severity in mental illness and constitute external markers for atypical brain development. Higher frequencies of MPAs can be found in children with autism. The aims of the present study were to examine the prevalence and patterns of MPAs in adults with autism spectrum disorder (ASD) and to investigate whether MPAs are associated with symptom severity and overall functioning. Fifty adults with ASD and intelligence within the normal range and 53 healthy controls were examined with the Waldrop scale, an instrument for assessing MPAs. Face and feet were photographed enabling blinded assessment. Significant differences between the ASD and the control group were found on the MPA total scores, and also in the craniofacial region scores. Moreover, the shape of the ears was associated with autistic traits, in the ASD group. High MPA total scores were associated with poorer functioning. The findings suggest a link between MPAs, autistic traits, and level of functioning. Assessment of MPAs may assist in the diagnostic procedure of psychiatric disorders.

Improved analysis of palm creases

Palm creases are helpful in revealing anthropologic characteristics and diagnosing chromosomal aberrations, and have been analyzed qualitatively and quantitatively. However, previous methods of analyzing palm creases were not objective so that reproducibility could not be guaranteed. In this study, a more objective morphologic analysis of palm creases was developed. The features of the improved methods include the strict definition of major and minor palm creases and the systematic classification of major palm creases based on their relationships, branches, and variants. Furthermore, based on the analysis of 3,216 Koreans, palm creases were anthropologically interpreted. There was a tendency for palm creases to be evenly distributed on the palm, which was acknowledged by the relationship between major and minor creases as well as by the incidences of major creases types. This tendency was consistent with the role of palm creases to facilitate folding of palm skin. The union of major palm creases was frequent in males and right palms to have powerful hand grip. The new method of analyzing palm creases is expected to be widely used for anthropologic investigation and chromosomal diagnosis.

Dermatoglyphic indices of males with the fragile X syndrome and of the female heterozygotes

Indices for males with the fragile X [fra(X)] syndrome and for the female heterozygotes have been established. The indices were based on the increased frequencies of whorls and radial loops on the third digits of affected males and heterozygous females, increased frequency of arches on the third digits of the affected males, and an excess of low ab ridge counts and abnormal palmar creases, particularly the Sydney crease, in both sexes. The indices were calculated using the logN odds ratio based on the frequencies of the above dermatoglyphics and palmar creases in 47 males with the syndrome compared to 497 male controls and 36 heterozygous females compared to 493 female controls. The indices had similar distributions in males and females. Seventy per cent of males with the syndrome and 67% of female heterozygotes had an index greater than or equal to +0.5. Thirty-one per cent of female heterozygotes who had both the dermatoglyphic index calculated and their chromosomes examined under appropriate conditions for the fra(X) site had an index less than +0.5 and had less than 2% fragile sites (most had none). However when the two tests were considered together, only 4/35 (11%) of the heterozygotes would not have been identified using the two criteria. The data suggest that the dermatoglyphic index is a helpful adjunct test with chromosome analysis for the identification of fra(X) heterozygotes.