There is a correlation between the presence of erythema nodosum leprosum and a reduction in the proportion of Treg-cells, as well as an increase in the CD4+ to CD8+ T-cell ratio. Additionally, there is an observed rise in the amount of interleukin-17 (IL-17)-producing T-cells. The initiation erythema nodosum leprosum reactions can be attributed to dysregulation of the immune system. This evidence concerns the gene CD4 and Erythema nodosum.