Candidate gene and genome-wide association studies have reported that single-nucleotide polymorphisms at different genomic loci are associated with androgenetic alopecia development. A number of genes determine the predisposition for androgenetic alopecia in a polygenic fashion. However, further studies are needed before the specific genetic factors of this polygenic condition can be fully explained.

<b><i>Introduction:</i></b> Physicians have largely studied the cutaneous involvement of coronavirus disease 2019 (COVID-19), but only few reports have focused on telogen effluvium (TE) as a possible sequela of COVID-19. We assessed 14 cases of hair loss occurring after SARS-CoV-2 infection using trichoscopy and trichogram to investigate patterns related to COVID-19. Furthermore, we discussed possible mechanisms involved in COVID-19 TE. <b><i>Case Presentation:</i></b> Fourteen individuals were referred to our post-COVID-19 dermatology office complaining acute hair loss after SARS-CoV-2 infection. Clinical evaluation included pull test, trichoscopy, and trichogram. CO­VID-19 TE occurred after a median of 2 months (range 1–3 months) following SARS-CoV-2 infection. The median duration of hair loss was 5 months (range 1–6 months). Trichoscopy showed variable but typical TE patterns. Trichogram showed different telogen/anagen ratio depending on the interval between onset of hair loss and trichological visit. <b><i>Discussion/Conclusion:</i></b> Our cases showed TE between 1 and 3 months after the onset of SARS-CoV-2 infection, thus earlier than classic TE. Trichoscopic features and trichogram showed no variations from classic TE. Different pathogenetic mechanisms including pro-inflammatory cytokines and direct viral damage on the hair follicle can be hypothesized; further studies on a larger sample are needed to better understand this condition.

Androgenetic alopecia (AGA) is a genetically determined progressive hair-loss condition which represents the most common cause of hair loss in men. The use of the medical term androgenetic alopecia reflects current knowledge about the important role of androgens and genetic factors in its etiology. In addition to androgen-dependent changes in the hair cycle, sustained microscopic follicular inflammation contributes to its onset. Furthermore, Prostaglandins have been demonstrated to have the ability in modulating hair follicle cycle; in particular, PGD2 inhibits hair growth while PGE2/F2a promote growth. Due to the progressive nature of AGA, the treatment should be started early and continued indefinitely, since the benefit will not be maintained upon ceasing therapy. To date, only two therapeutic agents have been approved by the Food and Drug Administration and European Medicines Agency for the treatment of AGA: topical minoxidil and oral finasteride. Considering the many pathogenetic mechanisms involved in AGA, various treatment options are available: topical and systemic drugs may be used and the choice depends on various factors including grading of AGA, patients' pathological conditions, practicability, costs and risks. So, the treatment for AGA should be based on personalized therapy and targeted at the different pathophysiological aspects of AGA.

Alopecia areata (AA) is an organ-specific autoimmune disorder that targets anagen phase hair follicles. The course is unpredictable and current available treatments have variable efficacy. Nowadays, there is relatively little evidence on treatment of AA from well-designed clinical trials. Moreover, none of the treatments or devices commonly used to treat AA are specifically approved by the Food and Drug Administration. The italian Study Group for Cutaneous annexial disease of the italian Society of dermatology proposes these italian guidelines for diagnosis and

Background Common COVID‐19 vaccines side effects are pain at the injection site, muscle pain, fever, headaches, fatigue. Possible immune‐related side effects in predisposed individuals have not been established so far. Materials and Methods We report three cases of recurrence of alopecia areata (AA) occurred after the first dose of COVID‐19 vaccine. Results All patients had previous episodes of AA with total hair regrowth and stable remission during the months preceding the vaccination. Rapid hair loss occurred 2‐3 weeks after BNT162b2 mRNA (patient 1) and AZD1222/ChAdOx1 vaccine (patient 2 and 3), with widespread hair loss in two cases and a single patch of the vertex in one case, with typical trichoscopic features of AA. Discussion Both BNT162b2 mRNA and AZD1222/ChAdOx1 vaccines share the same goal of inducing the immune system, with antibodies production and Th1 cells activation with release of pro‐inflammatory cytokines. Thus, in patients with pre‐existing inflammatory dysregulated pathways, the interaction between the immune system and vaccines may enhance other autoimmune mechanisms. In our cases, we speculate that vaccine may have induced the hair loss focusing on components having a key role in both COVID‐19 vaccination and AA pathogenesis. Conclusion This report may help to collect new data concerning possible immune‐related effects of vaccines. Certainly, only three cases are not sufficient to draw conclusion, thus a large‐scale study is necessary. Immune‐mediated side effects remain a rare event, thus the benefits of COVID‐19 vaccines outweigh the risk of disease flares and we strongly recommend it in all eligible patients with AA.