Commentary: Systemic Lupus Erythematosus in Native sub-Saharan Africans: A Systematic Review and Meta-Analysis

Abstract

Low and middle-income countries are thought to have a high frequency of infectious diseases and a low rate of autoimmune and allergic diseases (1); this belief has supported the "hygiene hypothesis, " i.e., the idea that a decreased incidence of infections contributes directly to an increased frequency of autoimmune and allergic diseases worldwide (2). In particular, the incidence of systemic lupus erythematosus (SLE) in black Africans has long been considered negligible (3). A recent systematic review and meta-analysis on SLE in native sub-Saharan Africans (4) challenges this view and changes the perspective. By examining studies published between January 2008 and October 2018 on SLE in native sub-Saharan Black Africans, the pooled prevalence of the disease among 28,575 participants in Internal Medicine and Rheumatology Units was found to be 1.7%. Patients were diagnosed between 1987 and 2014, and the mean age at diagnosis was 28.8-39.2 years (4). Studies from only 11 countries, the majority of which located in West Africa, were included in the analysis, and the pooled mortality rate was 10.3%, with infections, kidney disease, neurological involvement, and SLE flares as the main causes (4). The patients had 89.7% prevalence rate for antinuclear antibodies and 54.6% for anti-DNA antibodies, and a high seroprevalence for anti-ribonucleoprotein (57.9%), anti-Smith (53.5%), anti-Sjogren syndrome antigen A (45.6%) and anti-Sjogren syndrome antigen B (33.7%) autoantibodies (4). The high seroprevalence rates of ENA autoantibodies confirms their higher frequency in Blacks, due to genetic susceptibility (5). The authors outlined that the prevalence from their study contrasted with the low number of SLE cases described by Bae et al. (3) over 20 years before, in spite of comparable data sources and geographical coverage. Importantly, a review of published studies is different from a review of all cases diagnosed with SLE in all hospitals or in referral hospitals of certain countries over a defined period of time, and is likely to underestimate the real number of observed hospital cases. Three questions arise from the results of this review, that estimated a hospital-based prevalence in urban areas: is the rise in diagnoses due to improved diagnostic capacity of sub-Saharan African doctors, or to a real increase in the number of cases? What is the prevalence of SLE in the general population? Are other autoimmune diseases also more frequent than commonly thought?