and the Archives of Dermatology Temporal Case Clustering in Pityriasis Rosea

Objective: To detect temporal case clustering in pa-tients with pityriasis rosea in different geographic loca-tions. Design: Regression analysis of dates on which 1379 pa-tients were diagnosed as having pityriasis rosea in 3 dif-ferent geographic locations. The control data consisted of dates of diagnosis of patients with psoriasis in the same settings. Setting:Dermatology clinics in Kuwait, Minnesota, and Diyarbakir, Turkey. Patients:Patientswith pityriasis rosea and psoriasis seek-ing care in the clinics. Results: Three significant positive clusters (P=.005, P=.001, and P=.01, respectively) and 1 significant nega-tive cluster (P.001) were detected in these series of pa-tients. No cluster was detected in 2 corresponding se-ries of patients with psoriasis in Kuwait and Turkey. Conclusion: Temporal case clustering exists in pityria-sis rosea. Arch Dermatol. 2005;141:767-771 T HE CAUSE OF PITYRIASISrosea (PR) is unknown.Studies on the associationof PR with human herpes-virus 7 infection1-10 have yielded conflicting results. Recent stud-ies have reported no evidence of PR asso-ciated with cytomegalovirus, Epstein