Assessing the growth of children with spinal muscular atrophy using specific curves: A retrospective cohort study

Abstract Background Children with spinal muscular atrophy (SMA) do not follow standard anthropometric growth trajectories; disease‐specific curves were published in 2021. Our aim was to apply these in SMA children comparing their growth and body composition longitudinally, relative to the World Health Organization (WHO) standard. Methods This was a retrospective cohort of 19 SMA pediatric patients in a long‐stay hospital with monthly anthropometric measurements from admission to discharge. We calculated body mass index) and length‑for‑age z scores (BMIz and LAzs) using WHO and SMA‑specific curves. Triceps skinfold and mid‐upper arm circumference z scores (TSFz and MUACz) used WHO reference. Results Participants had a median age of 9 (IQR, 7–14) months, followed up for 19 months (IQR, 6.5–32). At admission, BMIz was −1.31 ± 0.66 by WHO and 0.77 ± 0.50 by SMA curves ( P < 0.01). According to WHO, 11 (57.9%) were malnourished, 8 (42.1%), eutrophic, and 0 overweight, but with SMA curves the comparable values were 2 (10.5%), 9 (47.4%), and 8 (42.1%), respectively. MUACz was −0.3 ± 0.7 and TSFz 2.01 ± 0.84. TSFz correlated better with BMIz based on SMA ( R 2 = 0.46) than with WHO curves ( R 2 = 0.27). Over time, BMIz remained stable, HAz rose slightly by both curves, MUACz showed a declining trend, and TSFz increased 0.38 annually ( R 2 = 0.34; 95% CI, 0.11–0.63; P = 0.006). Conclusion SMA‑specific growth curves assess better the nutrition status in children with SMA compared with WHO standards, aligning more closely with body composition. The cohort demonstrated increased fat accretion, normal length growth, and stable BMI over time.