We report phenotypic switching from atopic dermatitis to psoriasis in a 44‐year‐old man during treatment with upadacitinib. The patient also had experienced a similar course with dupilumab. This case exemplifies mutual antagonism between atopic dermatitis and psoriasis in predisposed individuals.

Immune checkpoint inhibitors (ICIs) are a relatively novel class of drugs whose administration has been approved for several malignancies. Adverse events are quite common, and the skin is the most frequently involved organ. In fact, regardless of the neoplasm being treated, more than 50% of patients receiving ICIs develop cutaneous immune-related adverse events (irAEs), with variable time to onset and severity. Potential pathogenetic mechanisms include drug-induced formation of neoantigens, unmasking of hidden selfantigens, and diffuse keratinocyte apoptosis induced by CD4+ and CD8+ T cell activation. Risk of cutaneous irAEs seems to be higher after anti-CTLA-4 rather than anti-PD-1/PD-L1 agent administration and rises in case of combination therapy. Furthermore, incidence of skin toxicity increases in the presence of specific malignancies (i.e., advanced melanoma) and pre-existing dermatoses or autoimmune diseases, while the possible role of ethnicity is still unclear. Aim of this review is to summarise the current knowledge of cutaneous irAEs and provide the clinician with a detailed clinical and histopathological description of the following types of skin toxicity: inflammatory dermatoses, immunobullous diseases, alterations of melanocytes, alterations of keratinocytes, hair abnormalities, oral and nail involvement. Particular attention is given to practical management of the different cutaneous irAEs, including detailed information about treatment regimens and necessity for ICI discontinuation. Patients should always receive multidisciplinary care, especially in severe or recalcitrant cases. The role of the dermatologists remains pivotal, particularly with regard to differential diagnosis and management of complex skin toxicity, as well as regular longterm follow-up of the patient's conditions.

(1) Background: Kaposi’s sarcoma (KS) is an angioproliferative neoplasm typically appearing as angiomatous patches, plaques, and/or nodules on the skin. Dermoscopy and ultrasonography have been suggested as an aid in the diagnosis of KS, but there is little evidence in the literature, especially regarding its possible differential diagnoses. Our aim is to describe and compare the clinical, dermoscopic, and ultrasonographic features of KS and KS-like lesions. (2) Methods: we conducted a prospective study on 25 consecutive patients who were first referred to our tertiary care center from January to May 2021 for a possible KS. (3) Results: 41 cutaneous lesions were examined by means of dermoscopy, Doppler ultrasonography, and pathology, 32 of which were KS-related, while the remaining 9 were lesions with clinical resemblance to KS. On dermoscopy, a purplish-red pigmentation, scaly surface, and the collarette sign were the most common features among KS lesions (81.3%, 46.9%, and 28.1%, respectively). On US, all 9 KS plaques and 21 KS nodules presented a hypoechoic image. Dermoscopic and Doppler ultrasonographic findings of KS-like lesions, such as cherry angioma, venous lake, glomus tumor, pyogenic granuloma, and angiosarcoma were also analyzed. (4) Conclusions: dermoscopy and Doppler ultrasonography can be useful to better assess the features of KS lesions and in diagnosing equivocal KS-like lesions.

Background occasional case reports have described the appearance of Kaposi’s sarcoma (KS) on previously unaffected skin after incidental or accidental injury, but the association is probably under-reported. Objectives to present a large case series of patients suffering from Koebner phenomenon (KP) in KS and describe their main epidemiological, clinical, and therapeutic features. Methods we have retrospectively analyzed our clinical and photographic records of 524 patients who had been diagnosed with KS between 2009 and 2021. Results 31 of 524 (6%) KS patients developed KP. Among these 31 patients, 24 (77%) had KS lesions after surgery, 4 (13%) after electrochemotherapy, laser therapy and cryotherapy, and 3 (10%) on areas affected by bullous diseases. Conclusions trauma, including surgery or other medical procedures, can trigger KS, underlying the importance of treatment options which cause the least injury to the skin.

Atopic dermatitis (AD) is a chronic or chronically relapsing inflammatory skin disease which results from a complex, multifaceted interaction between environmental factors in genetically predisposed patients. Epidermal barrier impairment, alteration of the cutaneous microbiota, effect of external antigens, neurosensory dysfunction, and inflammatory and immune dysregulation all play a pivotal role in inducing and maintaining AD lesions. AD significantly impacts the patient's quality of life and general well-being and is often associated with anxiety and/or depressive symptoms. Classical treatment options include topical corticosteroids and calcineurin inhibitors, phototherapy, and systemic immunosuppression with oral corticosteroids, cyclosporine, methotrexate, and azathioprine in more severe cases. A turning point in facing AD was accomplished when the efficacy and safety of dupilumab, a monoclonal antibody targeting the interleukin (IL)-4 receptor a subunit, led to its approval for the treatment of moderate-tosevere or severe AD in children, adolescents, and adults. Subsequently, a more extensive understanding of AD etiology and pathogenesis has allowed the development of several topical and systemic novel therapy options. Most of these drugs are monoclonal antibodies which interfere with the type 2 inflammatory cascade, especially its key cytokines IL-4 and IL-13, or its downstream Janus kinase signaling pathway. However, considering the relevance of other subtypes of T helper (Th) cells, such as Th1 and Th22, and the important role of specific cytokines (IL-31) in generating pruritus, the horizon of potential therapeutic targets has widened extremely. In this review, we aim to present the most promising systemic agents currently under investigation and illustrate the most significant aspects of their efficacy, safety, and tolerability.