Table 1.

Genome-wide DNA methylation studies in psoriasis.

Author (year)	Tissue/cells	N cases and controls	Major findings
Gervin (2013)57	CD4-positive and CD8-positive T-cells	54 (27 pairs of monozygotic twins discordant for Ps)	No significant difference in methylation status comparing discordant co-twins
Chandra (2018)59	Skin (psoriatic and adjacent normal)	39 Ps patients	Identification of differentially methylated CpG sites in several Ps susceptibility (PSORS) regions and inverse correlation between methylation and gene expression comparing psoriatic skin with adjacent normal skin
Roberson (2012)60	Skin (psoriatic, uninvolved and normal)	12 Ps patients and 10 controls	Identification of several differentially methylated CpG sites comparing psoriatic and control skin. With anti-TNF-α treatment, these methylation changes reverted back to baseline
Verma (2018)61	Epidermis (psoriatic, uninvolved and normal)	6 Ps patients and 6 controls	Identification of more than 2000 strongly differentially methylated sites with a striking overrepresentation of the Wnt and cadherin pathways
Gu (2015)62	Epidermis	12 patients undergoing narrow-band UVB phototherapy and 12 corresponding healthy controls	Identification of 3665 MVPs with an overall hypomethylation in Ps patient samples. DNA methylation pattern was reversed after successful phototherapy.
Zhou (2016)63	Skin (psoriatic, uninvolved and normal), peripheral blood mononuclear cells	114 Ps patients and 62 controls	Identification of several differentially methylated CpG sites comparing psoriatic skin to uninvolved skin and normal skin of healthy controls.

MVP, methylation variable positions; Ps, psoriasis.