Sister chromatid exchange in patients affected by severe psoriasis.

: An analysis of the sister chromatid exchanges has been carried out in lymphocytes from patients suffering from a severe form of psoriasis--pustular psoriasis (von Zumbusch), eruptive psoriasis vulgaris (more than 30% of the skin surface), severe arthropathic psoriasis and psoriatic erythroderma. These patients had never received treatment for their disorder. Our results, which show a normal level of sister chromatid exchanges in their blood cells, argue against the presence of a mutagenic factor in such patients.