(1) Background: A growing body of evidence highlights that intestinal dysbiosis is associated with the development of psoriasis. The gut–skin axis is the novel concept of the interaction between skin diseases and microbiome through inflammatory mediators, metabolites and the intestinal barrier. The objective of this study was to synthesize current data on the gut microbial composition in psoriasis. (2) Methods: We conducted a systematic review of studies investigating intestinal microbiome in psoriasis, using the PRISMA checklist. We searched MEDLINE, EMBASE, and Web of Science databases for relevant published articles (2000–2020). (3) Results: All of the 10 retrieved studies reported alterations in the gut microbiome in patients with psoriasis. Eight studies assessed alpha- and beta-diversity. Four of them reported a lack of change in alpha-diversity, but all confirmed significant changes in beta-diversity. At the phylum-level, at least two or more studies reported a lower relative abundance of Bacteroidetes, and higher Firmicutes in psoriasis patients versus healthy controls. (4) Conclusions: There is a significant association between alterations in gut microbial composition and psoriasis; however, there is high heterogeneity between studies. More unified methodological standards in large-scale studies are needed to understand microbiota’s contribution to psoriasis pathogenesis and its modulation as a potential therapeutic strategy.

Introduction An increased incidence of tinea capitis has been observed over the last few decades. Trichoscopy is a non-invasive, in-office method helpful in establishing the correct diagnosis in patients with hair loss and inflammatory hair disorders. The objective was to review and analyze current data on the trichoscopy of tinea capitis. Methods A systematic review of the literature was conducted using the PubMed, EBSCO and Scopus databases. The search terms included ‘tinea capitis’ combined with ‘trichoscopy’, ‘dermatoscopy’, ‘dermoscopy’, ‘videodermatoscopy’ or ‘videodermoscopy’. Results Of 326 articles, 37 were considered eligible for the quantitative analysis. The most characteristic (with a high predictive value) trichoscopic findings of tinea capitis included comma hairs (51%), corkscrew hairs (32%), Morse code-like hairs (22%), zigzag hairs (21%), bent hairs (27%), block hairs (10%) and i-hairs (10%). Other common, but not characteristic, trichoscopic features were broken hairs (57%), black dots (34%), perifollicular scaling (59%) and diffuse scaling (89%). Morse code-like hairs, zigzag hairs, bent hairs and diffuse scaling were only observed in Microsporum tinea capitis (8/29, 28%; 6/29, 21%; 4/29, 14% and 4/29, 14%, respectively). In Trichophyton tinea capitis, corkscrew hairs were more commonly detected compared to Microsporum tinea capitis (21/38, 55% vs 3/29, 10%). Conclusion The presence of characteristic trichoscopic features of tinea capitis is sufficient to establish the initial diagnosis and introduce treatment before culture results are available. Trichoscopy may be useful in distinguishing between Microsporum and Trichophyton tinea capitis.

Dysbiosis has been identified in many dermatological conditions (e.g., psoriasis, atopic dermatitis, systemic lupus erythematosus). One of the ways by which the microbiota affect homeostasis is through microbiota-derived molecules (metabolites). There are three main groups of metabolites: short-chain fatty acids (SCFAs), tryptophan metabolites, and amine derivatives including trimethylamine N-oxide (TMAO). Each group has its own uptake and specific receptors through which these metabolites can exert their systemic function. This review provides up-to-date knowledge about the impact that these groups of gut microbiota metabolites may have in dermatological conditions. Special attention is paid to the effect of microbial metabolites on the immune system, including changes in the profile of the immune cells and cytokine disbalance, which are characteristic of several dermatological diseases, especially psoriasis and atopic dermatitis. Targeting the production of microbiota metabolites may serve as a novel therapeutic approach in several immune-mediated dermatological diseases.

Alterations of intestinal microbiota play a significant role in the pathogenesis of psoriasis. Dysbiosis may cause disruption of the intestinal barrier, which contributes to immune activation by translocation of microbial antigens and metabolites. Intestinal fatty acid binding protein (I-FABP) serves as a biomarker of enterocyte damage. The aim of this study was to investigate clinical and metabolic factors affecting plasma concentration of I-FABP in patients with psoriasis. Eighty patients with psoriasis and 40 control subjects were enrolled in the study. Serum I-FABP (243.00 (108.88–787.10) vs. 114.38 (51.60–241.60) pg/ml, p < 0.001) and neutrophil to lymphocyte ratio (NLR; 2.59 (1.96–3.09) vs. 1.72 (1.36–47 2.11), p < 0.01) were significantly increased in patients with psoriasis compared to controls. A significant positive correlation was found between I-FABP and body mass index (BMI) (r = 0.82, p < 0.001), Psoriasis Area Severity Index (PASI) (r = 0.78, p < 0.001) and neutrophil to lymphocyte ratio (NLR) (r = 0.24, p < 0.001). Rising quartiles of I-FABP were associated with increasing values of BMI, PASI and NLR. The results of the logistic regression model confirmed an increased risk of higher disease severity with I-FABP concentration – odds ratio 3.34 per 100 pg/mL I-FABP increase. In conclusion, intestinal integrity in patients with psoriasis is affected by obesity, severity of the disease and systemic inflammation. The modulation of gut barrier may represent a new therapeutic approach for psoriasis.