Progression in longitudinal studies has been estimated at 0.5 points per year in a subsample of 28 patients with SPG4 (Rossi et al., 2022), 0.8 points per year in a subset of 21 patients with SPG5 (Schöls et al., 2017), significant worsening after 14 months in a sub-cohort of 11 patients with complex HSP (Regensburger et al., 2022), and 1.17 points in a subsample of 30 HSP patients (most with complex HSP and many without genetic confirmation of the diagnosis, Amprosi et al., 2023). The gene discussed is SPAST; the disease is hereditary spastic paraplegia.