Viral exanthem in COVID-19, a clinical enigma with biological significance.

Editor

Since December 2019, the COVID‐19 has spread throughout the world at a staggering speed. As of 30 March 2020, the confirmed case number has reached 693 224 globally and the COVID‐19 has claimed 33 106 lives. Current researches emphasize on understanding of transmission patterns, severity, clinical features and risk factors for infection, but the data remain limited.

Common clinical features of COVID‐19 reported include fever, cough, myalgia, fatigue, headache and diarrhoea. It is not uncommon for viral infections to cause skin rashes, for example, measles, rubella and dengue fever all cause viral exanthems. However, the prevalence and pattern of cutaneous involvement with COVID‐19 are unknown. Guan et al. described 2 (0.2%) patients developed skin rash in the 1099 patients enrolled. However, the study did not describe the detailed skin manifestation, cutaneous symptoms, timing of the symptom onset or their criteria to diagnose the skin lesions and enrolment into the dataset. Since viral exanthem is not uncommon in viral infections, we were curious about skin manifestations in COVID‐19. Meanwhile, we are keen to explore if there is a distinctive cutaneous feature that can help us differentiate coronavirus disease (COVID‐19) from other viral infections.

In Italy, COVID‐19 has claimed over ten thousand lives, including more than 60 doctors. We honour the efforts of the physicians, nurses and healthcare workers in fighting this pandemic in Italy. In their busy clinical schedules, Recalcati et al. in Italy elegantly reported the first large analysis on the skin manifestations of 148 COVID‐19 positive patients in Lecco Hospital. After excluding 60 patients who recently had new drug intake, the authors unveiled a range of cutaneous manifestations including erythematous rash, widespread urticaria and chickenpox‐like vesicles in 20.4% of all the remaining patients. The report brought up a couple of questions that we would like to investigate further. First, the analysis did not include patients with similar clinical symptoms, i.e. cough or fever, but were tested negative. Since COVID‐19 negative patients, likely with other viral infections, may also have similar skin manifestation as COVID‐19 positive patients do, the difference in the prevalence and morphology of skin rash between COVID‐19 positive and negative patients warrants comparisons. This would address whether the skin rashes of the three patterns described in the study (erythematous, urticarial and varicelliform) are specific to the COVID‐10. Second, it is crucial to measure the viral load in different time points before, during and after the skin rashes in future studies. Viraemia and the skin exanthem may have different time kinetics in different viral infections. For example, viraemia of the measles peaks at the onset of skin rash, whereas viraemia of the parvovirus B19 ends before the onset of skin rash. Hence, the dynamic viral load and its reference to skin rash can become a vital clinical clue for the clinicians to determine the optimal timing (before, during or after the skin rash) to collect the samples for molecular identification.

As we have observed the heavy burden of triage and shortage of essential medical goods posed by the outspread of COVID‐19, the introduction of an easy clinical assessment tool like classic COVID‐19 skin manifestation is a novel path to cope with the challenge that we are facing during the pandemic. However, this will take more studies to build up the validity and reliability. Dermatology’s outlook in the COVID‐19 is multidimensional, starting from the pathogenesis, public health issues to applying new technologies in clinical practice, the opportunities are infinite. Most importantly, we dermatologists as part of the medical community should contribute our unique perspective in the battle against this formidable pandemic.