Histopathological Findings Are Associated with the Clinical Types of Psoriasis but Not with the Corresponding Lesional Psoriasis Severity Index

BACKGROUND The assessment of the severity of psoriasis is often subjective because of the lack of quantitative laboratory diagnostic tools. Histopathological examination is the most commonly performed procedure for psoriasis diagnosis; however, it is usually descriptive. Thus, there is currently no quantitative method of determining psoriasis severity. The clinical types of psoriasis are correlated with the severity of the disease, and a lesional severity index, such as the psoriasis severity index (PSI), could be used as a quantitative tool for assessing gross severity. OBJECTIVE To correlate the histopathological findings of psoriasis with the PSI. METHODS Psoriatic lesions in 98 patients were evaluated. The lesions were classified into the guttate, papular, small plaque, and large plaque types according to morphology, and were scored according to the PSI. Ten common histopathological features of psoriasis were evaluated for correlation with gross severity. RESULTS The clinical types of psoriasis showed significant correlations with the histopathological severity. However, the PSI score showed no correlation with histopathological severity. CONCLUSION In the future, subjective gross assessment should be modified by using objective measuring devices with detailed scales, in order to correlate the findings with the histological severity.