This study aims to evaluate the safety, feasibility, and preliminary efficacy of autologous hematopoietic stem cell transplantation (ASCT) in the treatment of neurological damage associated with hereditary homocysteine remethylation disorders. Meanwhile, peripheral blood, cerebrospinal fluid, and related clinical samples will be prospectively collected before and after transplantation to dynamically monitor changes in immune reconstitution and neuroinflammatory biomarkers. The study intends to explore the impact of immune system resetting on disease progression and central nervous system immune microenvironment, providing evidence for subsequent precise patient stratification and optimized therapeutic strategies.