Multiple Sclerosis: Changing Trends in Latin Americans. Epidemiology and Regional Characteristics.

Abstract

Multiple Sclerosis (MS), a demyelinating autoimmune CNS disorder, affects the susceptible individual through a complex pathogenic process conditioned by interactions between genetics and environmental factors. MS prevalence has remarkably increased in Latin America (LATAM). Historical introduction of the European HLA genetic signature (DRB15) appears to be a determining element in the increasing propensity to the disease in the region. Other postulated contributing factors include accessibility to MRI technology, utilization of modern diagnostic criteria and increasing public awareness. Mestizos, a complex racial group resulting from centuries of admixture between white Caucasians of European origin, Amerindians (Asian/Mongoloid ancestry) and African genetics, constitute the predominant Latin American (LA) ethnic group being affected by MS, while non-mixed Amerindians appear to have an inheritable genetic resistance. Variable frequencies across the region may reflect lack of uniformity of the epidemiologic tools employed. There is no clear north/south gradient MS distribution in LATAM while the proposed theoretical protective role of exposure to Ultraviolet Solar Radiation (UVSR) and vitamin D concentration has not been established in these areas. The only potential environmental agent studied in depth in the region is Varicella-Zoster Virus (VZV) identified as the most prominent risk factor in MS cohorts from Central Mexico. No phenotypic differences with the “western” (Caucasian) forms of MS have been reported from clinical studies in LA. Neuromyelitis Optica (NMO) is the common differential diagnostic challenge in the Americas considering this disorder typically affects non-Caucasian populations. The “Asian” Opticospinal form of MS thought to be a common variant among LA, most likely represented NMO cases. Progress is been made in diagnostic ascertainments. The overall economic burden MS exerts to the health institutions in the Americas has become a realistic challenge to the developing economies in the region. Potential remedial actions are discussed.

Key Words: Multiple Sclerosis, Latin America, Mestizos, Neuromyelitis Optica.