Neuromyelitis Optica Spectrum Disorders in Africa

Abstract

Background and ObjectivesNeuromyelitis optica (NMO) is a CNS inflammatory disease that predominantly affects the optic nerves and the spinal cord. It is more frequent in Asian and African populations than in European ones. Data on epidemiology, clinical presentation, additional investigations, and treatment in the African continent are scarce. We aim to (1) collect and analyze published data on neuromyelitis optica spectrum disorder (NMOSD), (2) indicate challenges in the diagnosis and management, and (3) discuss opportunities for future research, education, and policy making, specifically on the African continent.MethodsA systematic review was performed in January 2021 with the search terms “Neuromyelitis optica and Africa,” “Devic Disease and Africa,” and “NMOSD and Africa.” We included all study types except case reports, correspondence, or conference abstracts on NMO or NMOSD. Extracted data included study design, country, study period, demographic and clinical characteristics, results of paraclinical investigations, and outcome. Data analysis was performed with descriptive statistics.ResultsWe retrieved a total of 79 records, of which 19 were included. Ten of 54 African countries reported a total of 410 cases. Almost half of them were from North African countries. The mean age at diagnosis was 33 years (range 7–88 years), and 75% were female. Transverse myelitis followed by optic neuritis were the most frequent symptoms at the time of presentation. One hundred nineteen patients experienced at least 1 previous relapse, and 106 had a relapsing course after diagnosis. Relapses were treated with IV methylprednisolone. Azathioprine and steroids were used most often as maintenance treatments. Outcomes were rarely described.DiscussionThe majority of studies on NMOSD from the African continent are retrospective, and most countries do not report any data. Our systemic review shows that data derived from patients living in Africa correspond well to what has been previously published in meta-analyses on patients of African ancestry with NMOSD who live outside of Africa, except for a younger age at onset and a lower proportion of females. We advocate for systematic data collection to adequately capture and monitor the burden of NMOSD, for expansion of research efforts and facilities to perform fundamental and clinical research, and for improved access to health care including diagnostics, treatments, and rehabilitation services for people affected by NMOSD in the African continent.

Prevalence of neuromyelitis optica spectrum disorder in the United States

“…7,22 Our findings suggest that a 28% of NMOSD patients may be Black Americans, which is more conservative than the 37% noted in a multicenter observational study of 187 patients seen at facilities in Baltimore, MD, Rochester, MN, and Dallas, TX, USA. 23 Also, our and other Afro-American prevalence estimates are remarkedly higher than those for African populations (0.004–0.2 per 100,000), 6 suggesting that genetic admixture and European ancestry may be a predisposing risk factor, which is similar to what has been observed in MS. 24,25 A notable difference with the more common MS (2018 age/sex-adjusted US prevalence 219 per 100,000) is that the prevalence of MS is higher in White Americans (284 per 100,000) than in Black Americans (226 per 100,000). 16 With respect to Asian Americans, our US prevalence estimates (9.4 per 100,000) were higher than those reported for country-specific Asian populations (e.g.…”

“…4 This rare disease affects all populations; however, the burden varies across geographic and racial/ethnic populations, from 0.004/1,000,000 in Ethiopia to 10/100,000 in Martinique, and it disproportionately affects females. 5–7 Within the United States, there have been two epidemiologic studies but unfortunately their prevalence estimates are remarkably different. In a landmark population-based study of residents of Olmsted County, Minnesota, the 2011 NMOSD age- and sex-adjusted prevalence was 3.9 per 100,000, with a higher prevalence in Black residents (13 per 100,000) than in White residents (4 per 100,000).…”

Big Data Analysis of Inflammatory Conditions Associated With Optic Neuritis

“…12,13 A study of NMOSD in Africa found that the NMO-to-MS ratio is higher in sub-Saharan Africa compared with northern African countries. 14 These studies from around the world highlight differences in the epidemiology, etiologies, and characteristics of ON and its associated diseases among different populations. In any case, it is critical to make the underlying diagnosis as early as possible and to initiate appropriate therapy to protect vision and reduce the risk of ON recurrence and other neurologic sequelae.…”