around one-third of people psoriasis report family history of disease, , researchers have identified genetic loci associated condition. identical twin studies suggest 70% chance of twin developing psoriasis if other twin has disorder. risk around 20% nonidentical twins. these findings suggest both genetic susceptibility , environmental response in developing psoriasis.
psoriasis has strong hereditary component, , many genes associated it, unclear how genes work together. of identified genes relate immune system, particularly major histocompatibility complex (mhc) , t cells. genetic studies valuable due ability identify molecular mechanisms , pathways further study , potential drug targets.
classic genome-wide linkage analysis has identified 9 loci on different chromosomes associated psoriasis. called psoriasis susceptibility 1 through 9 (psors1 through psors9). within loci genes on pathways lead inflammation. variations (mutations) of genes commonly found in psoriasis. genome-wide association scans have identified other genes altered characteristic variants in psoriasis. of these genes express inflammatory signal proteins, affect cells in immune system involved in psoriasis. of these genes involved in other autoimmune diseases.
the major determinant psors1, accounts 35%–50% of psoriasis heritability. controls genes affect immune system or encode skin proteins overabundant psoriasis. psors1 located on chromosome 6 in major histocompatibility complex (mhc), controls important immune functions. 3 genes in psors1 locus have strong association psoriasis vulgaris: hla-c variant hla-cw6, encodes mhc class protein; cchcr1, variant wwc, encodes coiled protein overexpressed in psoriatic epidermis; , cdsn, variant allele 5, encodes corneodesmosin, protein expressed in granular , cornified layers of epidermis , upregulated in psoriasis.
two major immune system genes under investigation interleukin-12 subunit beta (il12b) on chromosome 5q, expresses interleukin-12b; , il23r on chromosome 1p, expresses interleukin-23 receptor, , involved in t cell differentiation. interleukin-23 receptor , il12b have both been linked psoriasis. t cells involved in inflammatory process leads psoriasis. these genes on pathway upregulate tumor necrosis factor-α , nuclear factor κb, 2 genes involved in inflammation. recently, first gene directly linked psoriasis has been identified. rare mutation in gene encoding card14 protein plus environmental trigger enough cause plaque psoriasis (the common form of psoriasis).
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