Short communication Multiple sclerosis is associated with psoriasis. A case–control study Avi Fellner a , Marina Dano b , Keren Regev c , Amnon Mosek b , Arnon Karni c,d, ⁎ a Department of Neurology Belinson Hospital, Rabin Medical Center (AF), Israel b Headache Clinic, Tel Aviv Sourasky Medical Center, Israel c Neuroimmunology Clinic of the Department of Neurology, Tel Aviv Sourasky Medical Center, Israel d Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel abstract article info Article history: Received 15 June 2013 Received in revised form 25 November 2013 Accepted 2 January 2014 Available online 10 January 2014 Keywords: Multiple sclerosis Psoriasis Interferon-beta Autoimmune disease T cell mediated disease Co-morbid patients Background: MS and psoriasis are both autoimmune diseases putatively mediated mainly by T cells. Objective: We conducted a case control study to investigate whether patients with MS have a high rate of comorbid psoriasis. Methods: The cohort consisted of 214 consecutive MS patients and a control group of 192 consecutive patients with headache. Results: There was a higher than expected frequency of psoriasis among the MS patients. There was no gender effect and none of the 9 affected MS patients were among the 22 MS patients with primary progressive disease. Six of those 9 patients started interferon-β treatment after being diagnosed with MS, and 4 of them experienced exacerbation of psoriasis during exposure to interferon-β. There was no exacerbation in the co-morbid patients during treatment with other disease-modifying drugs. Conclusions: Our observation confirms other reports on an association of MS with autoimmune diseases and sup- ports the hypothesis of autoimmune pathogenesis for MS. The current findings should raise the level of awareness of psoriasis among patients with MS, and of the need to consider a potential exacerbation of psoriasis by interferon-β therapy. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Multiple sclerosis (MS) is considered to be an immune-mediated disease; however the exact immune mechanism of the disease is still unknown. There are many lines of evidence that support an immune etiology for MS, among them the pathological findings of immune activity in the disease-related lesions of the central nervous system [1], genetic association of patients with MS with immune-related genes [2], shared genetic alleles, as the immune-mediated disease risk single nucleotide polymorphisms (SNPs), with other immune-mediated diseases [3]. MS and psoriasis are both linked to genetics and immunological factors [4,5] and experimental animal studies showed that both diseases have aberrant induction of IFN-γ + Th1 cells and IL-17 + Th17 cells [6]. Auto- immune diseases tend to be clustered with other autoimmune diseases in the same patients or among family members [7]. Indeed, there are descriptions of association of MS with other autoimmune diseases in the same patients as well as in their family members [8,9]. Like in MS, psoriasis is considered to be a cellular immune-mediated disease [10] that includes different manifestations of lesion types. Psoriasis and MS were found to share a same genetic association with SNPs [2]. Treatment with fumaric acid was reportedly to be effective in both psoriasis and relapsing remitting (RR) MS [11,12]. Interferon-β therapy for RR MS was reported to induce exacerbation of psoriasis, and the up- regulation of type 1 interferon production was implicated in the patho- genesis of psoriatic skin lesions [13]. It has not yet been established whether there is an association between MS and psoriasis. We, here, re- port our study about the prevalence of psoriasis among patients with MS. 2. Methods 2.1. Participants A total of 214 consecutive MS patients (143 females, 71 males) who were seen for a period of 12 months in the Neuroimmunology Outpatient Clinic of the medical center were recruited. All patients fulfilled the 2010 diagnostic criteria of MS. The control group was comprised of 192 consec- utive patients with headache (124 females, 68 males) attending the medical center's Headache Clinic for a variety of diagnoses, and none suspected of having MS. We assumed that this population has no differ- ence in the rates of psoriasis as the general population (Table 1). Journal of the Neurological Sciences 338 (2014) 226–228 ⁎ Corresponding author at: Department of Neurology, Tel Aviv Sourasky Medical Center, 6 Weitzman St., Tel Aviv 64239, Israel. Tel.: +972 36974380; fax: +972 3 6947549. E-mail address: arnonk@tlvmc.gov.il (A. Karni). 0022-510X/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jns.2014.01.003 Contents lists available at ScienceDirect Journal of the Neurological Sciences journal homepage: www.elsevier.com/locate/jns