Central Nervous System Idiopathic Inflammatory Demyelinating Disorders in South Americans: A Descriptive,...

Area of Science:

• Neurology
• Immunology
• Epidemiology

Background:

• The idiopathic inflammatory demyelinating disease (IIDD) spectrum, including multiple sclerosis (MS) and neuromyelitis optica (NMO), exhibits varying frequencies across different ethnicities and geographic regions.
• South America's population is characterized by significant racial mixing due to colonization and historical migration patterns, necessitating an analysis of IIDD within this diverse context.

Purpose of the Study:

• To investigate the epidemiological and clinical characteristics of the IIDD spectrum in South America, considering the region's ethnic heterogeneity.
• To determine the relative frequencies of MS, NMO, and other related disorders within the South American population.

Main Methods:

• A cross-sectional, multicenter study involving 1,917 patients diagnosed with IIDD in 2011 across 22 centers in South America.
• Data collection included demographic, clinical, and laboratory information, with diagnoses confirmed using updated criteria.
• Analysis focused on disease categories, ethnicity, age of onset, disability progression (Expanded Disability Status Scale - EDSS), and NMO-IgG antibody status.

Main Results:

• Multiple sclerosis (MS) constituted 76.9% of IIDD cases, predominantly affecting white females. Neuromyelitis optica (NMO) represented 11.8% of cases, with a higher prevalence in individuals of African descent.
• NMO cases were more frequent in young African-Brazilian women and were associated with a relapsing-remitting course and moderate to severe long-term disability.
• While MS patients showed a correlation between disease duration and EDSS score, this was not observed in NMO patients. NMO-IgG antibody positivity was found in 58.6% of NMO cases.

Conclusions:

• Despite significant ethnic admixture in South America, MS predominantly affects white women, similar to Western populations, but with a notable proportion of non-white cases.
• NMO is a significant component of the IIDD spectrum in South America, disproportionately affecting non-white individuals, particularly women of African descent, and leading to greater disability.
• The study highlights a South-North gradient for NMO and non-white populations, reinforcing previous findings on the higher frequency of NMO in these groups.