A review of spinal muscular atrophy in black South African paediatric patients

Abstract

Background. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder that is present in all populations and results in muscle weakness owing to anterior horn cell degeneration. SMA is divided into three clinical subtypes and is an important genetic cause of morbidity and mortality but has not been well studied in sub-Saharan Africa.

Objective. This study aims to describe the clinical features and genetic findings in black patients with SMA presenting to the Division of Paediatric Neurology at Chris Hani Baragwanath Academic Hospital (CHBAH) over a 30-year period.

Method. This study was a retrospective review of patient records. The study population was black paediatric neurology patients with clinical SMA, who attended CHBAH Neurology Clinic between 1988 and 2018. Patients were categorised into SMA type 1, 2 or 3 based on their neurology assessment and clinical features were recorded.

Results. The clinical findings in the study population (with SMA), i.e. hypotonia, areflexia and tongue fasciculations, were similar to those found in international studies. More than half of the patients (65.6%; n=86/131) had genetic tests, of which 84.8% were positive for SMA. This value was significantly higher than previously reported results from South Africa. At least 23.6% (n=31/131) had facial involvement.

Conclusions. This study adds to the limited body of research on SMA in sub-Saharan Africa and highlights the lower frequency of a homozygous deletion seen in the black South African population compared with the expected 95% worldwide.