Type 2 inflammation is a fundamental immunologic pathway underlying a growing spectrum of dermatologic diseases. While classically associated with atopic dermatitis, type 2 immune responses are increasingly recognized as key contributors to prurigo nodularis, chronic spontaneous urticaria, bullous pemphigoid, lichen simplex chronicus, and other chronic pruritic disorders. Barrier disruption and epithelial injury initiate the release of alarmins, including thymic stromal lymphopoietin (TSLP), interleukin (IL)-33, and IL-25, which activate innate and adaptive immune pathways that promote type 2 inflammation. Subsequent production of effector mediators such as IL-4, IL-13, IL-5, IL-31, immunoglobulin E (IgE), and periostin drives barrier dysfunction, immune cell recruitment, tissue remodeling, and chronic pruritus. Increasing evidence further highlights the importance of neuroimmune crosstalk, with direct interactions between immune cells, cytokines, and sensory neurons contributing to itch sensitization and disease persistence. The clinical success of biologic therapies targeting IL-4/IL-13, IgE, and IL-31 signaling has provided powerful functional validation of these pathogenic pathways and has transformed the management of multiple inflammatory skin diseases. In this review, we summarize the molecular and cellular mechanisms underlying type 2 inflammation in the skin, discuss its role across diverse dermatologic conditions, and highlight emerging concepts in disease heterogeneity, neuroimmune signaling, and precision medicine. Collectively, these findings support type 2 inflammation as a unifying immunologic framework and therapeutically actionable target across dermatology.

Psoriasis is a chronic immune-mediated inflammatory dermatosis characterized by marked clinical heterogeneity. Although plaque psoriasis represents the most common phenotype, several uncommon and atypical variants may pose considerable diagnostic challenges because of their unusual morphology, distribution, and clinicopathological presentation. Early recognition of these rare forms is essential to avoid misdiagnosis and inappropriate management. This narrative review summarizes the current evidence regarding selected atypical variants of psoriasis, including psoriasis gyrata, linear psoriasis, follicular psoriasis, psoriatic onycho-pachydermo-periostitis, psoriatic neurodermatitis, interdigital psoriasis, parakeratosis pustulosa, psoriasis of the lips, psoriasiform acral dermatitis, psoriasis dermatitis, and extreme hyperkeratotic forms. For each entity, we discuss epidemiology, clinical presentation, dermoscopic and histopathological findings, differential diagnosis, pathophysiological hypotheses, and therapeutic considerations. Particular attention is given to distinguishing these entities from inflammatory, infectious, and neoplastic mimickers. The integration of clinical evaluation with dermoscopy and histopathological examination remains crucial in challenging cases. Awareness of these uncommon variants may improve diagnostic accuracy and facilitate timely therapeutic intervention.

Drug-induced hypereosinophilic syndromes (HESs) have been associated with a variety of medications, including biologic agents. We present a case of an 85-year-old female with a history of giant cell arteritis (GCA) complicated by ascending aortic aneurysm and aortitis, who developed marked peripheral eosinophilia (peaking at 3710/µL) and a persistent pruritic papular rash during long-term tocilizumab therapy. Extensive infectious, hematologic, and immunologic evaluations were unrevealing. While the clinical picture raised concern for a drug-induced hypersensitivity reaction, histopathology was more consistent with lichen simplex chronicus, and there was no evidence of systemic organ involvement. Her eosinophilia and cutaneous symptoms improved significantly after discontinuing tocilizumab, implicating the drug as a possible trigger. This case highlights the diagnostic challenges in distinguishing drug reaction with eosinophilia and systemic symptoms (DRESS) from other drug-induced or idiopathic dermatoses in patients receiving biologic therapy and underscores the importance of clinicopathologic correlation in guiding management.

Atopic dermatitis (AD) is a chronic, pruritic inflammatory skin condition with a complex pathogenesis and variable clinical presentation, often overlapping with other dermatologic diseases. This article considers the differential diagnoses for AD, emphasizing the importance of accurately distinguishing it from both common and rare conditions. Among inflammatory dermatoses, seborrheic dermatitis, psoriasis, allergic and irritant contact dermatitis, lichen simplex chronicus, and pityriasis rosea share overlapping features but can be differentiated based on history, distribution, and morphology. Infectious mimickers include scabies, tinea corporis, impetigo, and secondary syphilis, each with unique clinical or diagnostic markers. High priority diagnoses such as neoplastic diseases (mycosis fungoides), autoimmune conditions (dermatomyositis), nutritional deficiencies (zinc, niacin), genetic syndromes (Netherton, severe dermatitis-allergies-metabolic wasting), primary immunodeficiencies (hyper-IgE, DiGeorge, Wiskott-Aldrich syndrome), and drug eruptions require special consideration. Despite growing interest in immunologic and molecular biomarkers for AD, no single biomarker offers diagnostic certainty. Advances in diagnostic tools such as epidermal profiling and RNA sequencing may pave the way for more personalized approaches to dermatologic care. Currently, accurate diagnosis of AD remains clinical and requires vigilance, especially when disease course and response to therapy deviate from expected patterns.