The present invention relates to a device, system and method for managing treatment of an inflammatory autoimmune disease of a person. The proposed device comprises an input unit (20) for receiving measurement data acquired over time including white blood cell count data related to the person's white blood cell count, tumor necrotic factor-alpha data related to the person's tumor necrotic factor-alpha, C-reactive protein data related to the person's C-reactive protein, cortisol level data related to the person's cortisol level and melatonin data related to the person's melatonin concentration.The device further comprises a treatment manager (21) for managing treatment of the inflammatory autoimmune disease of the person by combining the obtained measurement data by an algorithm to obtaina disease activity level, to monitor the disease activity level over time and to determine treatment interventions based on the monitored disease activity level.