Subsequently, HSP-SPAST (SPG4), HSP/ATX-SPG7 (SPG7) as well as ATX-ATXN1 (SCA1), ATX-ATXN2 (SCA2), ATX-ATXN3 (SCA3), ATX-CACNA1A (SCA6), ATX/HSP-SACS (ARSACS), and Alexander’s disease (GFAP) were excluded. The gene discussed is HSP90B2P; the disease is Alexander disease.