SPG20 encodes a protein that contains a MIT (Microtubule Interacting and Trafficking molecule) domain. This protein may be involved in endosomal trafficking, microtubule dynamics, or both functions. Frameshift mutations associated with SPG20 cause autosomal recessive spastic paraplegia 20 (Troyer syndrome). Troyer syndrome (SPG20) is a complicated type of hereditary spastic paraplegias (HSPs). HSP is a category of neurological disorder characterized by spasticity and muscle weakness in the lower limbs.