Although limited data exists regarding IL-9 alteration with aging and neurodegeneration, a curious finding was reported by Wharton et al. (2019), indicating that elevated CSF IL-9 levels were only associated with African American AD patients, and consistently in two separate large cohorts, post-mortem brain IL-9-related molecular markers were also present only in African-American AD subjects. The gene discussed is IL9; the disease is Alzheimer disease.