The cellular source of CHI3L2 has not been clarified in ALS; however, CSF CHI3L2 was parallelly elevated with CSF CHI3L1, which is related to neuroinflammation and expressed in microglia of the spinal cord of patients with ALS (19, 20, 22, 37). This evidence concerns the gene CHI3L1 and amyotrophic lateral sclerosis.