Minor physical anomalies are morphological abnormalities of cranio-fascial region and limbs that indicate deviant morphogenesis during early development of the fetus. Various genetic and environmental factors are considered to be important in their genesis. Abnormal dermatoglyphics and abnormal palmar creases are one of the minor physical anomalies commonly seen in persons with mental retardation.12 Palmar creases are formed during the early development of fetus i.e. between 7 to 14 weeks of gestation. Any alteration in developing hands and brain during morphogenesis would lead to abnormal palmar creases and mental retardation.
In our study we had observed that majority of the children with mental retardation had mild level of mental retardation i.e. 65%, while moderate, severe and profound levels of mental retardation contributed 18%, 10% and 7% respectively. These findings are consistent with the earlier studies from the West where mild mental retardation constituted the major subgroup and profound mental retardation the smallest. Similar trend is seen in the study from developing country Nepal.
A major focus of our study was to find the prevalence of different palmar crease patterns in children with mental retardation and to compare those with normal children. Our findings suggest an overall prevalence of abnormal palmar creases to be 45% in the case group and 15.5% in the control group and the difference was statistically significant in terms of abnormal palmar creases. Detailed analysis of patterns of palmar creases revealed that the normal palmar crease pattern was the most prevalent pattern in both groups.
The simian crease was found to be the most prevalent abnormal palmar crease followed by the Sydney crease and Suwon crease in children with mental retardation. It is in keeping with the findings of previous studies from the West that also report that normal palmar creases are more prevalent than abnormal palmar creases and the incidence of normal palmar creases is higher in persons with mental retardation as compared to their healthy counterparts. 17,18,19,20 Studies from India also report similar results i.e.
The simian crease is the most frequent abnormal palmar crease followed by the Sydney crease in children with mental retardation. A study by Kiran et al in children with mental retardation found that the incidence of Simian crease was 72.4% in males and 54.2 % in females while the incidence of Sydney line was 19.75% in males and 41.7% in females. The investigators concluded that incidence of Simian line and Sydney line is higher in children with mental retardation, and Simian line being more prevalent than Sydney line.21
We further tried to analyze any correlation between severity of mental retardation and different palmar crease patterns. Though there was a statistically significant correlation found for the same in the right palm, but the same finding was not present for the left palm. This differential finding of more lateralization of abnormal palmar creases to right palm can be attributed to the small sample size.
Further, the case group was constituted mainly by the children with mild mental retardation (65%) and children with other levels of mental retardation (35%) represented only small subsets of the group. So it is possible that if we had larger sample of severe forms of mental retardation, results could have reflected more of such associations. To our best of the knowledge no work is done in this particular area. To get more promising results large sample size should be evaluated.
