VP.14 Growth patterns in treated SMA children in the UK

Abstract

Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by degeneration of alpha motor neurons in the spinal cord. SMA type 1 (SMA1) is the most severe form, with patients never achieving sitting, whilst patients with SMA type 2 (SMA2) are sitters who are not able to walk independently. Disease modifying treatments such as nusinersen, onasemnogene abeparvovec, and risdiplam have led to increases in motor function and life expectancy. However, not much is known about the effect of these treatments on growth. The aim of this retrospective study was to analyse the patterns in weight, height, and BMI of treated SMA1 and SMA2 patients compared with the UK90 reference population. Cross-sectional data on growth was obtained from the SMA Research and Clinical Hub UK (SMA REACH UK) national database. Results are based on last available measurements of SMA1 (n=57) and SMA2 (n=41) nusinersen treated children. Median age was 3.02 (IQR: 1.44-4.78), and 6.93 (IQR: 4.73-8.81) years for SMA1 and SMA2, respectively. The results showed that compared to the paediatric normative data, SMA1 and SMA2 had a lower weight with the median weight z-score of -0.96 (IQR: -1.97; -0.16) and -1.20 (IQR: -2.02; 0.16), respectively. SMA2 children presented with a lower median height z-score (-1.37 (IQR: -2.19; -0.22)), compared to those with SMA1 (-0.91 (IQR: -2.28; 0.83)). Consequently, median BMI z-score was -0.90 (IQR: -2.82; 0.80) for SMA 1, and -0.63 (IQR: -1.46; 1.45) for SMA2 patients. Approximately a quarter of the children in this group are considered underweight (Weight SD score <=-2) for both SMA1 (25%) and SMA2 (27%). Children with SMA2 are more likely to be overweight (BMI SD score >=2) than patients with SMA1, with rates of 15% and 4% respectively. This analysis sheds light on how growth is affected by novel disease modifying treatments in SMA.