Low familial risks for multiple sclerosis in Buenos Aires, Argentina Mauricio F. Farez a, ⁎, María E. Balbuena Aguirre a,b , Francisco Varela a , Alejandro A. Köhler a , Vanesa Nagel a , Jorge Correale a, ⁎⁎ a Department of Neurology, Raúl Carrea Institute for Neurological Research (FLENI), Buenos Aires, Argentina b Department of Neurology, Hospital de Clínicas José de San Martín, Buenos Aires, Argentina abstract article info Article history: Received 13 June 2014 Received in revised form 26 July 2014 Accepted 4 September 2014 Available online 16 September 2014 Keywords: Multiple sclerosis Familial risk Argentina South America Recurrence risk Sibling recurrence-risk Background: Multiple sclerosis is a complex disease in which genetic susceptibility plays a role and familial occur- rence has long been recognized. To date, no studies of familial occurrence have been conducted in Argentina, a country with low to intermediate prevalence. Methods: As part of a cross-sectional study on multiple sclerosis in Buenos Aires, immediate and extended ped- igree details were collected on 219 patients. Crude and age-adjusted recurrence risks for patient relatives were also assessed. Results: Details on age or age of death and disease status were obtained for 4227 relatives. Ten percent of patients reported at least one relative with MS diagnosis, the highest risk (1.54%) was observed in daughters of patients who presented 92-times greater risk than the general population. Sibling recurrence risk ratio was similar to that reported in other locations. Conclusions: Relatives of patients with MS living in Argentina are at greater risk of developing the disease, although not as high as the risk reported for other geographic regions. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Multiple sclerosis (MS) is an inflammatory demyelinating disease caused by an autoimmune response targeted against the central ner- vous system, which is presumed to result from a complex interplay be- tween genetic and environmental factors [1]. Familial aggregation is one of the most recognized features of MS, and several studies have been published describing the increased risk of developing MS in mono or di- zygotic twins, offspring, siblings, half-siblings and even parents of dif- ferent genetic origin of MS patients [2–5]. Evidence shows that MS is a disease with complex genetic inheritance accounting for 30–35% of the risk of developing the disease in monozygotic twins [6]. The remain- ing risk is presumed to derive from interactions between several envi- ronmental cues such as vitamin D [7], smoking [8], obesity [9] and Epstein Barr virus (EBV) infection [10]. A commonly used measure for genetic susceptibility is sibling recurrence-risk (SRR) [11]. The relative risk or λ s , is a simple calculation that divides SRR by risk in the general population, a figure estimated to be between 12–80/100,000 inhabitants in Argentina [12]. Most previ- ous studies in other regions established this value between 12–40 for MS [13]. Several studies on familial MS in Europe [2], North America [14] and Australia [13] have been published, but no such study to the best of our knowledge, has been conducted anywhere in South America. Of note, the region has certain demographic peculiarities such as populations with different genetic backgrounds and admixture, with lower overall prevalence of MS compared to most other Caucasian populations [12]. Determining familial MS is of interest to estimate familial recurrence risk, and to advise patients in terms of individual family risk. To this end, local evidence is needed. We therefore set out to establish familial MS prevalence and MS recurrence risk for patients living in Buenos Aires, Argentina. 2. Materials and methods 2.1. Setting This study was conducted at the MS Clinic of the Raúl Carrea Institute for Neurological Diseases, in Buenos Aires, Argentina (location 34°S, 58°W). 2.2. Patients All MS patients defined according to 2010 McDonald criteria [15] attending our center were invited to participate in a cross-sectional sur- vey, the Argentina Case–Control Study on Multiple Sclerosis (Spanish acronym, EMECCA). Patients needed MS diagnosis confirmation from our center, and to be at least 18 years old to participate. If a patient Journal of the Neurological Sciences 346 (2014) 268–270 ⁎ Corresponding author. ⁎⁎ Correspondence to: Raúl Carrea Institute for Neurological Research, FLENI, Montañeses 2325, Buenos Aires 1428, Argentina. Tel.: +54 11 5777 3200x2704; fax: +54 11 5777 3209. E-mail address: jcorreale@fleni.org.ar (J. Correale). http://dx.doi.org/10.1016/j.jns.2014.09.004 0022-510X/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of the Neurological Sciences journal homepage: www.elsevier.com/locate/jns