Background: Adult Onset Stills Disease (AOSD) and Kikuchi Fujimoto Lymphadenitis (KFL) are both rare Rheumatological diseases. Co-occurrence is very rare. Case Presentation: This is a case of AOSD and KFL co-occurrence presenting with polyarthritis, rash, and B Symptoms. Elevated serum lactate dehydrogenase and ferritin with anemia and lymphadenopathy raised suspicions of lymphoma. Histology confirmed KFL and clinical features, and raised ferritin confirmed AOSD. After starting sulfasalazine, the patient was admitted to the hospital with ‘Drug Reaction with Eosinophilia and Systemic Symptoms’ (DRESS) Syndrome. Prior to sepsis exclusion, Gentamicin was given and subsequent hearing loss was noted. Sustained remission was achieved with Tocilizumab and azathioprine. Tocilizumab was stopped during pregnancy. Conclusion: The diagnostic challenges of two rare overlapping Rheumatological diseases are highlighted. An early distinction of disease flares or drug reactions from sepsis is difficult. Risk-benefit ratio consideration of continuing successful treatments in pregnancy is acknowledged.

Keywords: Case report, adult onset still disease, Kikuchi Fujimoto lymphadenitis, rare rheumatology diseases, DRESS syndrome, sulfasalazine, Disease Modifying Anti-Rheumatic Drugs, anti-tumour necrosis factor, interleukin (IL)-1 inhibition, IL-6 inhibition.