1. ^*Chair of Human and Medical Genetics, Department of Biopathology, "Tor Verngata" University of Rome, Italy;
2. ^†Department of Paediatrics, Medical Geneitcs Unit, University of Padova, Italy;
3. ^‡Department of Dermatology, Catholic University of Rome, Italy;
4. ^§VIII Dermatology Division, Istituto Dermatopatico dell'Immacolata, IRCCS, Rome, Italy;
5. ^¶CSS Hospital, IRCCS San Giovanni Rotondo, Italy

Correspondence: Professor Giuseppe Novelli, Cattedra di Genetica Umana, Dipartimento di Biopatologia e Diagnostica per Immagini, Università di Roma "Tor Vergata," Via di Tor Vergata 135, 00133 Roma, Italy

Received 5 January 1998; Revised 12 October 1998; Accepted 13 October 1998.

Abstract

Psoriasis is a chronic inflammatory dermatitis, affecting 2% of the population. Major clinical features include red, scaly patches on scalp, elbows, and knees, with or without severe arthritis. Several putative susceptibility loci have been mapped by parametric and non-parametric linkage analysis to chromosome regions 2p, 4q, 6p, 8q, 16q, 17q, and 20p; however, the most significant results and confirmation of linkage are only available for the 17q and 6p chromosome regions at present. In this study, 22 multiplex Italian families were investigated for linkage to 6p and 17q susceptibility regions, using a set of four microsatellites. These analyses failed to detect significant linkage with any of the examined markers. A genome-wide scan was then performed on one of the largest pedigrees, searching for an additional susceptibility locus. This study disclosed a putative linkage to chromosome 1cen-q21 markers. When these microsatellites were analyzed in the remaining families of the sample, a significant linkage was observed using both parametric and non-parametric methods. The highest two-point lod score value was obtained with D1S305 marker (3.75 at  = 0.05). Non-parametric analysis at this locus also demonstrated a significant excess of allele sharing (p = 0.0001).