COVID-19 in a patient with new adult-onset Still disease: A case report.

RATIONALE: Adult-onset Still disease (AOSD) is a systemic autoinflammatory illness of unknown cause. Its manifestations comprise fever; arthritis or arthralgia; and skin rash with high inflammatory markers and ferritin levels. Coronavirus disease 2019 (COVID-19) shares several clinical features and laboratory markers of AOSD: making it challenging to differentiate between the 2 conditions.

PATIENT CONCERNS: A 29-year-old woman presented with fever, skin rash, and polyarthritis 4 weeks before admission. Two weeks after illness onset, she had an infection with symptoms similar to those of COVID-19. She observed that her symptoms worsened, and new symptoms appeared including headache; vomiting; diarrhea; and loss of taste and smell. The patient tested positive for severe acute respiratory syndrome coronavirus 2 using polymerase chain reaction.

DIAGNOSIS: The patient was diagnosed with AOSD complicated with COVID-19 after exclusion of other possible causes of her illness, such as infections, malignancy, or underlying rheumatological disease.

INTERVENTIONS: The patient was administered corticosteroids and methotrexate. The patient responded quickly, particularly to corticosteroids.

OUTCOMES: This is the second reported case of COVID-19 in a patient with AOSD. She experienced COVID-19 shortly after having AOSD, indicating that those with AOSD might have a higher risk of COVID-19 infection. Furthermore, she developed the most prevalent COVID-19 symptoms. However, distinguishing most of these symptoms from AOSD manifestations was difficult.

LESSONS: Early diagnosis and differentiation between AOSD and COVID-19 and prompt initiation of treatment are required.