Study reveals overlapping features of giant cell arteritis,
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This article describes the distinct and overlapping features of giant cell arteritis (GCA) and COVID-19. Researchers performed 2 systemic literature reviews looking at reports of GCA and COVID-19 published prior to April 5, 2020. They identified 35 GCA studies and 29 COVID-19 studies and reviewed the frequency of clinical features for each disease.

Giant cell arteritis and COVID-19 share similar clinical features, albeit at varying degrees. Headaches were more prevalent in GCA versus COVID-19 (66% vs. 10%) whereas jaw claudication or visual loss were only reported in GCA (43% vs. 0%). Patients in both groups experienced fatigue, which was slightly more common among patients with COVID-19 (43% vs. 38%). Elevated inflammatory markers tended to occur more often in GCA than COVID-19 (elevated CRP, 100% vs. 66%), however platelet count was also dramatically elevated in GCA (47% vs. 4%). Features more common with COVID-19 than GCA included cough (63% vs. 12%), fever (83% vs. 27%) and lymphopenia (53% vs. 2%). Gastrointestinal upset was noted in a small proportion of COVID-19 and GCA patients (8% vs. 4%). Although alterations of smell and taste have been described in GCA, the frequency of these features is unclear.

These COVID-19 studies mainly assessed hospitalized patients and most inpatients were admitted due to respiratory issues. This may have led to overrepresenting certain COVID-19 symptoms such as cough and underrepresenting other symptoms relative to the larger, general community of patients with COVID-19. One cannot assume that symptoms not reported are truly absent. Having said that, this paper is still clinically valuable because the most prominent features of a disease are often the ones reported.

Clinical significance
This report points to the importance of keeping an open mind when patients visit ophthalmologists for GCA, particularly during the pandemic. Giant cell arteritis and COVID-19 might have overlapping symptoms with similar initial presentations such as headaches, fever, elevated levels of inflammatory markers (CRP) and cough. Visual loss and jaw claudication occur in GCA but have not been reported in COVID-19. Thrombocytosis might point the diagnosis more towards GCA, and lymphopenia towards COVID-19. Physicians should be aware of this potential diagnostic confusion.