Ashy dermatosis, also known as erythema dyschromicum perstans, is an acquired benign disease, characterized by blue-gray pigment patches with erythematous borders. The cause is still unclear, but probably has an immunologic basis.

The aim of this study was to determine gene frequencies of the HLA-DR alleles in Mexican patients with ashy dermatosis and compare them with ethnically matched healthy control subjects to reveal the genetic susceptibility to develop ashy dermatosis.

We included 23 consecutive patients with clinical and histopathologic confirmed diagnosis of erythema dyschromicum perstans. Patients and control subjects received a questionnaire to determine their ethnic origin and a peripheral blood sample was taken for DNA extraction. Finally, Genetic HLA-DRB1 was performed by polymerase chain reaction sequence-specific oligonucleotide reverse dot blot hybridization.

Of the 23 patients included in this study, 65% were women and 35% were men. We observed that the disease was located in the trunk in 17 patients (74%) and the upper limbs in 15 patients (65%). The most frequent allele was HLA-DR4 (65%) (pC < 1 × 10⁻⁶, odds ratio = 6.0, 95% confidence interval = 2.8-12.7) whereas in control subjects it was 23%. The most frequent molecular subtype in both patients and healthy control subjects was DRB10407, being statistically significant after comparing the two groups (pC < 1 × 10⁻⁶, odds ratio = 7.0, 95% confidence interval = 3.1-15.8).

Since this is a disease strongly influenced by ethnicity, extrapolation to other ethnic groups is limited.

Many factors influence the ethiopathogenesis of erythema dyschromicum perstans, but it is strongly suggested to have an important genetic susceptibility conferred by genes located within the major histocompatibility complex region.