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COVID-19, caused by the coronavirus SARS-CoV-2, has become pandemic. A further level of complexity opens up as soon as we look at diseases whose pathogenesis and therapy involve different immunological signaling pathways, which are potentially affected by COVID-19. Medical treatments must often be reassessed and questioned in connection with this infection. This article summarizes the current knowledge of COVID-19 in the light of major dermatological and allergological diseases. It identifies medical areas lacking sufficient data and draws conclusions for the management of our patients during the pandemic. We focus on common chronic inflammatory skin diseases with complex immunological pathogenesis: psoriasis, eczema including atopic dermatitis, type I allergies, autoimmune blistering and inflammatory connective tissue diseases, vasculitis, and skin cancers. Since several other inflammatory skin diseases display related or comparable immunological reactions, clustering of the various inflammatory dermatoses into different disease patterns may help with therapeutic decisions. Thus, following these patterns of skin inflammation, our review may supply treatment recommendations and thoughtful considerations for disease management even beyond the most frequent diseases discussed here., (© 2020 The Authors. Journal der Deutschen Dermatologischen Gesellschaft published by John Wiley & Sons Ltd on behalf of Deutsche Dermatologische Gesellschaft.)

Skin lesions associated with internal malignancy may present as cutaneous metastases or as typical lesions occurring in the context of certain cancer-associated genetic syndromes. Paraneoplastic syndromes, on the other hand, are only indirectly associated with an underlying malignancy and are not malignant per se. Historically, a distinction has been made between "obligate" and "facultative" paraneoplastic disorders, depending on the likelihood with which they are potentially associated with malignancy. In addition, there are nonspecific cutaneous manifestations that are only rarely associated with an underlying malignancy. Another possible classification is based on the pathophysiological mechanisms underlying the cutaneous lesions. In everyday practice, it is essential that dermatologists recognize potentially cancer-associated dermatoses, as this will frequently contribute to the initial diagnosis of an underlying neoplasm., (© 2020 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.)

Patients with Sézary syndrome (SS) show clonal expansion in the peripheral blood of skin-homing CD4+ T-helper cells expressing cutaneous lymphocyte antigen (CLA). However, an increase of CLA+ CD4+ T cells can also be observed in various inflammatory dermatoses. To facilitate early diagnosis and therapeutic monitoring of SS using flow cytometry, we evaluated the expression of CD7 and CD26 on the CLA+ CD4+ lymphocyte subset. Peripheral lymphocytes from 7 patients with SS, 16 patients with mycosis fungoides (MF) and 11 healthy controls were analysed by flow cytometry for the expression of CD4, CD7, CD26, CLA and CCR4. In addition, a longitudinal study was performed over 16 months in two patients with SS. Absence of CD7 and CD26 on CLA+ CD4+ T cells was highly specific for SS. Importantly, the absence of CD26 on CLA+ CD4+ T cells was very sensitive for SS, at 100% in our patient cohort. The number of CD26− CLA+ CD4+ T cells closely correlated with therapeutic interventions in the longitudinal analysis of two patients over more than 1 year. We conclude that the absence of CD26 expression on skin-homing CLA+ CD4+ T-helper cells is a very sensitive and highly specific parameter for early diagnosis and therapeutic monitoring of patients with SS. [ABSTRACT FROM AUTHOR]

Adhesion molecules and chemokine receptors are involved in tissue-specific homing of T cells to the skin and play an important role in the pathophysiology of cutaneous lymphoma. It has recently been reported that the chemokine CCL27 expressed by keratinocytes attracts lymphocytes bearing the chemokine receptor CCR10.To investigate the expression of CCR4, CCR7 and CCR10 on skin-homing CLA+ and CD4+ T cells in the peripheral blood of patients with Sézary syndrome (SS), a rare leukaemic variant of cutaneous T-cell lymphoma.Lymphocytes from five patients with SS, six patients with mycosis fungoides and four healthy volunteers were isolated and analysed using flow cytometry. Additionally, the T-cell receptor (TCR)-Vβ CDR3 regions were cloned and sequenced in two patients.We found that CCR4 is expressed on almost all CLA+ and CD4+ memory T cells. Using monoclonal antibodies specific for single TCR-Vβ chains we identified malignant T cells in four patients with SS. Importantly, we found that most but not all malignant Sézary cells expressed the skin-homing chemokine receptor CCR10. Additionally, we found that a significant proportion of these cells also expressed the lymph node-homing chemokine receptor CCR7.Our results support the concept that chemokine receptors play an important role in the pathophysiology of SS and suggest that the malignant clone may represent an expansion of skin-homing cutaneous‘central’ memory T cells in the peripheral blood of these patients. [ABSTRACT FROM AUTHOR]