SMA is generally regarded by clinicians as a motor-neuron disease but animal models of SMA and necropsies of pediatric patients with severe SMA show hepatic microvesicular steatosis. Since impaired hepatic function may result in significant future comorbidities and accrual of drug toxicity, finding non-invasive ways to detect and monitor hepatic pathology in SMA patients is important.

This is a single-center retrospective cohort study. All pediatric and adult SMA patients without any past medical history of liver disease, who were seen physically in clinic from 2020-2021, and who had received hepatic sonography, were included in the study (N=5). The sonographic steatosis grade was determined by an ultrasonogapher. Liver enzymes and serum markers of liver synthetic function were reviewed.  

Mild to moderate hepatic steatosis was present in 100% of SMA patients who received hepatic sonography, regardless of age and therapy regime. Three were adults aged 19, 24 and 52, and two were children aged 3 and 6. The adults received risdiplam and/or nusinersen, and the children had received nusinersen and onasemnogene abeparvovec-xioi or all 3 therapies. Liver enzymes were raised in two adults. Serum albumin, protein and INR were normal in all.

Sonographic evidence of hepatic steatosis may be frequent in SMA and may be a more sensitive measure of liver abnormality as compared to liver enzymes or serum markers of liver synthetic function. Next steps will be to use clinical and translational studies to understand how liver pathology contributes to the overall pathology of SMA and affects drug metabolism.