[An attempt to determine the variability of thermal phenotypes in monozygotic twins]

All solid bodies emit electromagnetic radiation at temperatures above absolute zero. The radiation spectrum depends, among other factors, on temperature. Thermovision is a method in which an infrared camera is used to record infrared radiation (IR) emitted by human skin. It is widely used in medicine, for instance to diagnose inflammation of the skin, some types of neoplasms, collagenosis, and peripheral vascular disease. The literature, however, lacks reports on the variability in thermal emission by the skin of healthy individuals or twins. Interpretation of the results is based on simply analysing the subject individually or comparing symmetrical body sides. Hence, there is a need to study thermal emission using monozygotic twins as a model.

An attempt was made in the present study to determine the variability of thermal phenotypes of faces, backs, and hands in monozygotic twins (MZ), compare thermal emission in MZ and dizygotic twins (DZ), and establish the thermal norm. Using the ThermaCAM SC500 camera, 44 pairs of MZ and 15 pairs of DZ were studied. Descriptive statistics are given as means, standard deviation, and max. and min. values. The following tests were used for statistical analysis: Shapiro-Wilk's, Snedecor's, Brown-Forsythe's, Mann-Whitney's U, and Kruskal-Wallis. Data from the digital image analyser were tested using the cluster analysis methods, especially the k-means method.

The following conclusions were drawn: 1. Full genetic identity does not produce a thermal consistency within the range of isotherms tested, whether in relation to their values or distribution. 2. Differences in the thermal image may have their source in ontogenetic development during intra-uterine and postnatal stages and may be related to individual differences in adaptation to the environment. 3. These results are potentially useful to compare physiological states between individuals and to differentiate pathological changes. 4. The results of this study do not allow for any conclusions regarding the thermal norm. However, a basis has been created for further research in larger samples of the population.