An audit of the epidemiological, clinical features and outcomes of patients with Neuromyelitis  Optica Spectrum Disorder (NMOSD) attending a South African Tertiary referral Hospital

Gule, Manqoba

An audit of the epidemiological, clinical features and outcomes of patients with Neuromyelitis Optica Spectrum Disorder (NMOSD) attending a South African Tertiary referral Hospital

Thesis / Dissertation

2023

Abstract

NMOSD is a severe CNS inflammatory disorder classically characterised by recurrent bouts of optic neuritis and myelitis. The pathogenic anti-aquaporin-4 antibody is present in most cases and distinguishes it from other forms of inflammatory CNS demyelination. This biomarker has led to recognising a broader clinical spectrum of NMOSD. Another recently discovered antibody, the anti-myelin-oligodendrocyte-glycoprotein-antibody, further broadens the spectrum of pathophysiological mechanisms and clinical presentations of NMOSD. NMOSD may be associated with infections, autoimmune diseases, and malignancies. Observational data from South Africa suggests an association between NMOSD and tuberculosis. Ethnicity and geographic locality play an important role in the epidemiology of NMOSD. Worldwide, non-European, particularly Black-African and Asian ethnicity, is associated with the highest incidence, prevalence and severity of NMOSD. Despite this, sub-Saharan African studies are under-represented in the medical literature. NMOSD is typically associated with aggressive attacks, which may recur, often in temporal clusters. When left untreated, NMOSD may result in severe permanent disability and death. Immune-based therapies are used to manage acute attacks and prevent recurrences. These include steroids and plasmapheresis, steroid-sparing agents, and large-molecule biological agents. Novel and highly effective disease-modifying treatments are continually being developed and examined in clinical trials. These agents are expensive, restricting their use in low-and middle-income settings. The prevalence of NMOSD in the study population remains unknown, nor is there local data on the clinical spectrum or whether an infectious trigger such as TB or HIV plays a role. This audit evaluated the characteristics of a cohort diagnosed with NMOSD attending a South African tertiary hospital. These included demographic, clinical, serological, radiologic, and therapeutic interventions and patient outcomes. We highlight serious shortcomings in case recognition and referral pathways. In our setting, NMOSD is under-recognised at district care facilities where 67% (26/39) of early NMOSD attacks presented and were not recognised. A further 38% (15/39) had recurrent admissions with unrecognised attacks. Moreover, 51% of patients with AQP4-Ab-positive serology captured by the PGWC Data Centre did not attend the referral neurology service. The demographic profiles of our cohort were similar to others that have been reported. Most of our patients were young women of non-European ancestry: Mixed-race (Coloured) and Black-African ethnicity. HIV and antecedent or concurrent tuberculosis were the most common comorbidities. At the neurology service, the AQP4-Ab-positivity rate was lower than compared with international cohorts. This was compounded by 20% of cases diagnosed with NMOSD despite not meeting diagnostic criteria. This raises the possibility of misdiagnosis and inappropriate management. Plasmapheresis is a highly effective, albeit expensive, treatment for acute attacks. Only 30% of patients were treated with plasmapheresis. The most frequently cited reasons were limited access and cost. Although understandable in low-and-middle-income settings, advocating for effective, equitable treatments materially affects patient outcomes. Robust local evidence of the disease burden and overall cost implications of relapses and subsequent disability will support this objective. Data from this, and other similar audits, will inform the development of evidence-based and cost-effective practices to guide immunotherapy and management strategies for NMOSD in resource-limited settings. Word Count: 495

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Medicine

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