Demographic and clinical correlates of extent of psoriasis during stable disease and during flares in chronic plaque psoriasis

Abstract

Following a previous population-based study, we define a common psoriatic phenotype (A) with a limited area of involvement of stable disease but extensive flares and a less common phenotype (B) with consistently widespread disease. To define these phenotypes quantitatively and to investigate any biological significance through correlations with clinical disease characteristics. Psoriatic plaque thickness was also included in the analyses. Two hundred and ninety-four patients who had had chronic plaque psoriasis for at least 5 years were recruited. Area of involvement during stable disease (A(basal)) and during the most severe flare (A(max)) were derived from current area of involvement and patient history. Mean plaque thickness (T) was calculated from a current Psoriasis Area and Severity Index score. Multivariate regression of each variable on A(basal), A(max) and T showed many highly significant relationships. Usually A(basal) and A(max) were retained in the final models but with some variables only A(basal) was retained, suggesting an intrinsic effect unrelated to A(max). Phenotype A was associated with female gender, age at onset < 40 years, exacerbation by sore throat and stress, decreased concern about psoriasis and good response to ultraviolet B and methotrexate. A(basal) was individually associated with nail and joint involvement and need for second-line therapy. T was related to male gender, nail involvement and decreased exacerbation by stress on univariate analysis but only to nail disease on multivariate analysis. The phenotypes have been shown to have biological significance. A(basal) and A(max) may be useful therapeutic indices of long-term severity in clinical trials and in the investigation of genetic/environmental influences on psoriasis severity.