## 3 Results
### Impact of SARS-CoV-2 Infection on psoriasis Clinical Course  
All selected studies are reported in Table 1.  
Figure 1: Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) on COVID-19 and psoriasis. From: [PERSON] [PERSON], [PERSON] [PERSON], [PERSON] [PERSON], [PERSON] [PERSON], [PERSON] [PERSON], [PERSON] [PERSON], et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. _BMJ_ 2021, 372, n71. doi: 10.1136/bmj.n71 For more information, visit: [[http://www.prisma-statement.org/](http://www.prisma-statement.org/)]([http://www.prisma-statement.org/](http://www.prisma-statement.org/)). Beyond the evidence that COVID-19 can present with cutaneous involvement, a growing concern about the potential exacerbation of preexisting psoriasis following COVID-19 emerged since the beginning of the pandemic. Viral infections are known to trigger the induction and exacerbation of psoriasis, and several mechanisms have been proposed to explain this process: antigen mimicry, epitope spreading, cytokine imbalance, and amplification of tissue destruction that increases the availability of self-antigens. In addition, SARS-CoV-2 infection is characterized by an overreaction of the immune response that could potentially shift the delicate immune balance in psoriasis [4]. A recent systematic review evaluated presentations, post-infection changes in the manifestation, diagnosis, and management of flare-ups of underlying dermatologic disease in patients with COVID-19. Authors reported nine patients with psoriasis and COVID-19, the flare-ups in five cases were attributed to either hydroxychloroquine or systemic corticosteroids which were initially considered promising treatments for COVID-19, and are well-known causes of drug-induced psoriasis [4]. The exacerbation of psoriasis in two cases could have resulted from the discontinuation of treatments (secukinumab and cyclosporine). In one case the COVID-19 treatment was not mentioned, the exacerbation of psoriasis in only one case could be confidently linked to COVID-19. In the literature, cases of development and exacerbation of pustular psoriasis (PP) during COVID-19 infection have also been reported [5; 6; 7; 8]. [PERSON] et al. described a case of a 62-year-old woman with a positive family history of psoriasis who developed a new PP 2 weeks after resolution of symptoms of SARS-CoV-2 infection [5]. An additional case of a patient who developed a pustular psoriasis flare following SARS-CoV-2 infection was described in November 2020. To be fair, the patient had been taking hydroxychloroquine before the flare, but given that he had taken the drug in the past without any consequences for psoriasis, the authors attributed the PP flare to the viral infection [6]. Then, [PERSON] et al. described a 60-year-old male patient with a childhood history of psoriasis who developed generalized PP (GPP) 26 days after the onset of initial COVID-19 symptoms [7]. Finally, [PERSON] et al. reported the case of a 62-year-old patient with a history of Acrodermatitis of Hallopeau who developed pustular psoriasis after SARS-CoV-2 infection [8; 9]. Thus, of all the cases in the literature, only a few can be assumed to have psoriasis induced by SARS-CoV-2 infection. This is not surprising, as viral infections have always been considered possible triggers of psoriasis onset [1]. Some authors hypothesize that psoriasis