Motor neuron disease in black African patients at a tertiary care hospital in Soweto, South Africa.

INTRODUCTION: In this brief report, we describe the nature of ALS in a South African cohort of patients of Black African ancestry - a population which has been historically understudied. METHODS: We performed a chart review of all patients attending the ALS/MND clinic at the Chris Hani Baragwanath Academic Hospital in Soweto, Johannesburg, South Africa, during the period 1 January 2015 to 30 June 2020. Cross-sectional demographic and clinical data captured at the time of diagnosis was collected. RESULTS: Seventy-one patients were included in the study. Males constituted 66% (n = 47), with a male to female sex ratio of 2:1. The median age at onset of symptoms was 46 years (IQR 40-57) with a median disease duration at diagnosis (diagnostic delay) of 2 years (IQR 1-3). The onset was spinal in 76% and bulbar in 23%. The median ALSFRS-R score at time of presentation was 29 (IQR 23-38.5). The median ALSFRS-R slope (unit/month) was 0.80 (IQR 0.43-1.39). Sixty five patients (92%) were diagnosed with the classic ALS phenotype. Fourteen patients were known to be HIV positive, and of those, 12 were on antiretroviral treatment (ART). None of the patients had familial ALS. CONCLUSION: Our findings of an earlier age at symptom onset and seemingly advanced disease at presentation in patients with Black African ancestry support the existing literature on the African population.

The mutational profile in a South African cohort with inherited neuropathies and spastic paraplegia.

Introduction: Limited diagnostics are available for inherited neuromuscular diseases (NMD) in South Africa and (excluding muscle disease) are mainly aimed at the most frequent genes underlying genetic neuropathy (GN) and spastic ataxias in Europeans. In this study, we used next-generation sequencing to screen 61 probands with GN, hereditary spastic paraplegia (HSP), and spastic ataxias for a genetic diagnosis. Methods: After identifying four GN probands with PMP22 duplication and one spastic ataxia proband with SCA1, the remaining probands underwent whole exome (n = 26) or genome sequencing (n = 30). The curation of coding/splice region variants using gene panels was guided by allele frequencies from internal African-ancestry control genomes (n = 537) and the Clinical Genome Resource's Sequence Variant Interpretation guidelines. Results: Of 32 GN probands, 50% had African-genetic ancestry, and 44% were solved: PMP22 (n = 4); MFN2 (n = 3); one each of MORC2, ATP1A1, ADPRHL2, GJB1, GAN, MPZ, and ATM. Of 29 HSP probands (six with predominant ataxia), 66% had African-genetic ancestry, and 48% were solved: SPG11 (n = 3); KIF1A (n = 2); and one each of SPAST, ATL1, SPG7, PCYT2, PSEN1, ATXN1, ALDH18A1, CYP7B1, and RFT1. Structural variants in SPAST, SPG11, SPG7, MFN2, MPZ, KIF5A, and GJB1 were excluded by computational prediction and manual visualisation. Discussion: In this preliminary cohort screening panel of disease genes using WES/WGS data, we solved ~50% of cases, which is similar to diagnostic yields reported for global cohorts. However, the mutational profile among South Africans with GN and HSP differs substantially from that in the Global North.