Multiethnic lupus cohorts: What have they taught us? Cohortes multiétnicas de Lupus: ¿qué nos han enseñado?

Systemic lupus erythematosus (SLE) is a heterogeneous multisystemic autoimmune disease of unknown etiology of variable course and outcome. It affects predominantlywomen (9:1) on their reproductive age years but can occur at the extremes of life (from infants to nonagenarians). In older adults the disease is not very severe, yet because it occurs in persons who may already have other comorbidities it tends to have less than a favorable outcome. In children, adolescents and young adults the disease tends to be more serious than in middle age adults. It is more frequent andmore serious among non-Caucasian population groups around the world.1,2 Although it is not completely understood why there are differences in the incidence and prevalence of SLE in these populations and why its outcome is less than favorable, the fact of the matter is that differences do exist; it has become clear that biologic and non-biologic factors act in concert to predispose to this disease and to modulate its outcome. The study of multiethnic lupus cohorts may provide some insight on how these factors interplay. The concept of ethnicity (as opposed to race) encompasses not only the ancestral genes for the respective population group but also a number of socioeconomic, cultural and geographic features which characterize each one of them. In the USA, for example, Hispanics or those individuals originating from a Spanish-speaking country and African descendants (including Afro-Caribbean and African Americans) tend to be socially disadvantaged in comparison to the Caucasianmajority. Moreover, even within these ethnic groups substantial biological and cultural differences do exist, as the proportion of ancestral genes (European, Amerindian and African within a three-hybrid model of inheritance) and the social context in which these groups have come about in the USA vary considerable; in the case of Hispanics, for example, older but also more educated immigrants may have a legally recognized status whereas a high proportion of the more recent immigrants,many ofwhomare poorly educatedmay be illegal, may differ considerably. Thus ascribing differences in disease expression between ethnic groups only to these groups’ genetic