TFRC and hereditary spastic paraplegia: In patients with HSP, gut microbiota dysbiosis and associated metabolic alterations are linked to impaired intestinal barrier integrity, activation of the innate immune system, and dysregulation of adaptive immune cell subsets; this includes imbalances in the T helper 17 (Th17)/regulatory T (Treg) and follicular helper T (Tfh)/follicular regulatory T (Tfr) axes.