Numerous plasmacytoid dendritic cell infiltration in HIV-associated psoriasis relieved only with antiretroviral therapy

Histopathological analysis of skin reactions after coronavirus disease 2019 vaccination: Increment in number of infiltrated plasmacytoid dendritic cell

Skin disorders are frequent adverse events after coronavirus disease 2019 (COVID-19) vaccination. However, the pathogenesis of these disorders is not fully understood. Here, we report a case series of cutaneous adverse events following COVID-19 vaccination, and the results of our investigation reveal the underlying mechanism. Case 1: a 47-year-old female developed a wheal, confined to the COVID-19 vaccination site, 2 days after her first injection. She was treated with topical steroids and oral antihistamines. Case 2: a 51-year-old female showed generalized petechial erythema accompanied by fever, genital bleeding, thrombocytopenia, liver dysfunction, and disseminated intravascular coagulation, 2 days after her second injection. She was diagnosed with vaccine-induced macrophage activation syndrome and treated with anti-inflammatory therapy. Immunohistological analysis of the skin eruption, in both these cases, showed infiltration of CD123⁺ BDCA2⁺ plasmacytoid dendritic cells (p-DC). Despite the distinctive clinical features in these two cases, this finding suggests that p-DC might be involved in different cutaneous adverse events after COVID-19 vaccination.

Skin Mycobiome of Psoriasis Patients is Retained during Treatment with TNF and IL-17 Inhibitors

Background: Biological treatment relieves refractory skin lesions in patients with psoriasis; however, changes in the fungal microbiome (the mycobiome) on the skin are unclear. Methods: The skin mycobiome of psoriasis patients treated with TNF inhibitors (TNFi, n = 5) and IL-17 inhibitors (IL-17i, n = 7) was compared with that of patients not receiving systemic therapy (n = 7). Skin swab samples were collected from non-lesional post-auricular areas. Fungal DNA was sequenced by ITS1 metagenomic analysis and taxonomic classification was performed. Results: An average of 37543 reads/sample were analyzed and fungi belonging to 31 genera were detected. The genus Malassezia accounted for >90% of reads in 7/7 samples from the no-therapy group, 4/5 from the TNFi group, and 5/7 from the IL-17i group. Biodiversity was low in those three groups. Few members of the genus trichophyton were detected; the genus Candida was not detected at all. Among the Malassezia species, M. restricta was the major species in 6/7 samples from the no-therapy group, 4/5 from the TNFi group, and 5/7 from the IL-17i group whose the other largest species revealed M. globosa. Conclusions: The mycobiome is retained on post-auricular skin during systemic treatment with TNF and IL-17 inhibitors.