Researchers at Technische Universitat, Munich, and other centers in Germany, studied the prevalence of KIR4.1-IgG by ELISA in 47 children with acquired demyelinating disease (ADD), in 22 with other neurologic diseases, 22 with autoimmune disease, and in 18 healthy controls. Serum antibodies to KIR4.1 were identified in 57% of children with ADD but none with other neurologic disease, autoimmune disease or healthy controls. KIR4.1-IgG titers were predominantly found in children with MS or clinically isolated syndrome and in 1 in 3 with demyelinating encephalitis, similar to the prevalence in adults with ADD. KIR4.1-IgG titers were significantly higher in children with ADD compared with control groups (p < 0.0001); they were not age-dependent and did not correlate with myelin oligodendrocyte glycoprotein (MOG) antibody responses. MOG-IgG occurs before age 10 y in ADD whereas KIR4.1 antibodies are found in older children and adult patients with MS. 
COMMENTARY. KIR4.1, a potassium channel expressed on oligodendrocytes and astrocytes, contributes to the maintenance of the electrochemical gradient by removing potassium from the extracellular space. Mutations of the KIR4.1 gene cause EAST syndrome characterized by epilepsy, ataxia, sensorineural deafness, and tubulopathy . The prevalence of KIR4.1-IgG in children with MS is similar to adults.