SPG11 and hereditary spastic paraplegia: sTREM2 has demonstrated utility in other neurodegenerative diseases as a marker of microglial activation and phagocytic function, and although not yet studied in HSP, it represents a promising candidate for capturing neuroinflammation in subtypes like SPG11 and SPG15, detecting subclinical disease activity in presymptomatic carriers, and stratifying patients based on immune-glial engagement.