Atopic dermatitis in skin of colour. Part 1: new discoveries in epidemiology and pathogenesis

Atopic dermatitis (AD) is a global condition that has a rising prevalence in developing countries such as those within South-east Asia and Latin America. Recent research represents the condition as a heterogeneous disease of distinct endotypes among different ethnic groups. Variation between ethnic groups in physiological measures such as transepidermal water loss, ceramide/+, skin sensitivity, alongside pathological barrier and immune system dysfunction processes, may ultimately lead to the distinct phenotypes seen clinically. AD in patients of White ethnicities is typified by filaggrin dysfunction, more T helper (Th)1 and less Th17 involvement, with less epidermal thickness compared with patients of Black or Asian ethnicities. AD in patients of Black ethnic groups is Th2/Th22-skewed, with robust IgE expression, and less Th1 and Th17 involvement than patients of Asian or White ethnicities. AD across South Asian and East Asian populations is characterized by Th17/Th22 upregulation. Differences also exist in how AD psychosocially has an impact on individuals of different ethnic groups.