## 3 Results
### Impact of psoriasis on SARS-CoV-2 Infection  
All studies selected for this topic are summarized in Table 2.  
Skin has been described as one of the most common involved target organ in SARS-CoV-2 infection [11]; however, whether and how psoriasis is influenced by SARS-CoV-2 infection is still unclear, as published studies are rare and conflicting. First, [PERSON] et al. hypothesized a strict connection between psoriasis and COVID-19 disease focusing their attention on the role of angiotensin-converting enzyme (ACE). In humans, ACE2 receptor is widely expressed in the lung, heart, kidney, endothelium and intestine, and also in the basal epidermal layer and sebaceous gland cells in normal skin [22]. It has already been demonstrated that SARS-CoV spike protein has a strong binding affinity to the human ACE2 receptor, and this could explain why skin may be a possible specific target for the SARS-CoV-2, which in fact can be also isolated from skin specimens [11; 23; 24; 25; 26]. Moreover, serum level of ACE is increased among psoriasis patients, and directly correlates with increased risk of cardiovascular comorbidities, including subclinical atherosclerosis [27]. In patients with severe psoriasis (e.g., erythroderric) the increased ACE skin activity decreases after UVB treatment [28]. Conversely, the ACE inhibitors administration in patients with personal history of psoriasis may be associated with psoriasis exacerbation [22]. The link between ACE2 receptor and SARS-CoV-2 could result in ACE2 downregulation and in over-production of angiotensin by the ACE enzyme, the opposing physiological homolog of ACE2 [12]. Overall, the overexpression of ACE in COVID-19 patients may aggravate psoriasis favoring also cardiovascular complications, particularly in patients with severe psoriasis [13]. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Type of Study [Reference]** & **Outcomes** &
\begin{tabular}{c} **Number of** \\ **Patients** \\ \end{tabular} & **Results** \\ \hline Reviews, meta-analysis [11; 12] & The role of angiotensin converting enzyme in the link between psoriasis and risk of the COVID-19 & NA & Psoriasic patients may be at an higher risk of worsening cardiovascular events in case of COVID-19 infection \\ \hline Epidemiological analysis [13] & Genome-wide association study transdisease meta-analysis between COVID-19 susceptibility and two skin diseases ( psoriasis and atopic dermatitis). & 435,019 patients & Having an inflammatory skin disease decreased the risk of requiring mechanical ventilation \\ \hline Reviews, meta-analysis, National Psoriasis Foundation guidelines [14; 15; 16; 17; 18; 19; 20; 21] & Prognostic factors of COVID-19 outcome in psoriatic patients & NA & Severity of COVID-19 is primarily driven by smoking status, sex (male), older age, and underlying comorbidities; Age, male sex, and pre-existing comorbidities are crucial drivers for poor COVID-19 outcome in patients with psoriasis \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Impact of psoriasis on SARS-CoV-2 infection. NA: not applicable. According to [PERSON] et al., psoriasis patients may be at a higher risk of worsening cardiovascular events in case of COVID-19 infection [22; 29]. These findings, however, failed to be confirmed by subsequent studies. [PERSON] et al. [30] published an epidemiological analysis of 435,019 patients managed in Michigan Medicine (formerly the University of Michigan Health System) who had at least one health system encounter between 1 January 2019 and 20 June 2020. Authors made a genome-wide association study on transdisease meta-analysis between COVID-19 susceptibility and two skin diseases (psoriasis and atopic dermatitis). People affected by an inflammatory skin disease have increased risk of being infected with SARS-CoV-2. Differently from results of [PERSON] et al. [22], having an inflammatory skin disease decreased the risk of requiring mechanical ventilation [30].