Interleukin (IL)-17A is produced in a varied percentage of rheumatoid joint synovia [12, 13], with evidence suggesting that the presence of IL-17A is both predictive of disease progression in RA [12] and contributes to the inflammation by synergising with the actions of other key inflammatory mediators such as IL-1β, IL-6 and TNF-α [14, 15]. The gene discussed is IL17A; the disease is rheumatoid arthritis.