It has been previously reported that levels of CHIT1 are elevated in ALS CSF and that CHIT1 protein can induce motor neuron loss when injected into rat neonates.28 Although higher CHIT1 levels in sALS CSF were confirmed in our study, our filtration studies excluded CHIT1 as the neurotoxic candidate since both 100 and 300 kDa-filtered sALS CSF which retained the 51 kDa CHIT1 protein had no effect on motor function or motor neurons upon injection into the cervical subarachnoid space. The gene discussed is CHIT1; the disease is amyotrophic lateral sclerosis.