Psoriatic plaque thickness is a clinical measure of psoriasis severity. We have observed that patients tend to revert to a baseline thickness of psoriatic plaques when in an untreated state, and hypothesized that other features of psoriasis could associate with this trait. Data prospectively collected on 500 participants in the Utah Psoriasis Initiative were used for the study. In response to a question assessing plaque thickness when disease was at its worst, 144 (28.8%) reported thick plaques, 123 (24.6%) reported thin plaques, and 233 (46.6%) reported intermediate thickness. For patients with "worst-ever" disease at enrollment (n=122), there was significant correlation of thickness between assessment by the patient and the physician (r=0.448, P-value 0.01). Thick plaques associated with male gender, increased body mass index, nail disease, psoriatic arthritis, larger plaques, more body sites, and greater total body surface area affected. Thin plaques associated with eczema, guttate psoriasis, and skin cancer. We suggest that this is preliminary evidence that plaque thickness is an easily measured trait that associates with other clinical features of psoriasis, and that stratification on this phenotype may be useful in further defining the genetic basis of this disease.

We report the use of non-invasive tape stripping to sample psoriatic lesional and non-lesional skin in 96 patients. The procedure was well tolerated with any discomfort described as mild; we did not observe any cases of Koebner phenomena at any non-lesional tape-stripped sites. Tape-harvested epidermis was extracted for RNA, which was profiled by semiquantitative reverse transcriptase-PCR. This analysis revealed that mRNAs for tumor necrosis factor alpha, IFNgamma, Krt-16, CD2, IL-23A, IL-12B, and vascular endothelial growth factor are overexpressed in the "average" psoriatic lesion in a majority of patients. In addition, 10 of these patients were biopsied at lesional and non-lesional sites and the expression data compared to tape-stripping data. This comparison shows that five of seven mRNA are more highly expressed in cells captured by tape stripping than biopsy, suggesting that the upper aspect of a lesion contains cells very active in the disease. The tape-harvesting data reveal that approximately 46% of lesions have at least one pathogenic mRNA within non-lesional skin limits. Data demonstrate that tape stripping reveals mRNA markers not detected in biopsy samples and thus the method may be a useful supplement to biopsy.

Using a patient's baseline plaque morphology to choose a primary treatment modality may result in earlier disease improvement and reduce the cost of therapy.

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