Rosacea is a chronic inflammatory facial dermatosis with four main phenotypes: erythematotelangiectatic (ETR), papulopustular (PPR), phymatous (including rhinophyma), and ocular rosacea. Pathophysiology includes dysregulated innate immunity, Demodex proliferation, neurovascular hyperreactivity, and barrier dysfunction. Management is phenotype-based: vascular lasers and topical…
Acne vulgaris is a common chronic disorder of the pilosebaceous unit characterized by comedones, inflammatory papules/pustules, and nodules that can lead to scarring and dyspigmentation. Pathogenesis involves follicular hyperkeratinization, excess sebum production (androgen-mediated), Cutibacterium acnes dysbiosis and inflammation, and neuroendocrine/immune…
Pyoderma gangrenosum is a rare, neutrophilic dermatosis presenting as rapidly progressive, painful ulcers with undermined violaceous borders. Pathergy is characteristic. PG is frequently associated with systemic diseases (IBD, arthritis, hematologic disorders). Diagnosis is clinical and by exclusion; biopsy supports a…
Hidradenitis suppurativa (HS) is a chronic, relapsing inflammatory disease of hair follicles in intertriginous regions, characterized by painful nodules, abscesses, double-ended comedones, sinus tracts, and scarring. Pathogenesis involves follicular occlusion, dysregulated innate/adaptive immunity (IL-1, TNF, IL-17 axes), microbiome shifts, mechanical…
Sarcoidosis is a multisystem granulomatous disease characterized by noncaseating granulomas. Cutaneous sarcoidosis occurs in up to one-third of patients and may be the initial or sole manifestation. Skin lesions are polymorphic, including papules/plaques, lupus pernio, scar or tattoo infiltration, subcutaneous…
Cutaneous vasculitis encompasses a spectrum of disorders characterized by vessel wall inflammation resulting in purpura, nodules, ulcers, and livedoid changes. Small-vessel neutrophilic vasculitis—classically leukocytoclastic vasculitis (LCV), also termed cutaneous small-vessel vasculitis (CSVV)—presents with palpable purpura on dependent areas. Etiologies include…
Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by pathognomonic cutaneous findings and variable muscle, lung, and systemic involvement. Cutaneous dermatomyositis (CDM) may occur with minimal or absent myositis (clinically amyopathic DM). Hallmark rashes include heliotrope erythema, Gottron papules/sign, photosensitive…
Cutaneous lupus erythematosus (CLE) encompasses a spectrum of lupus-specific skin diseases that may occur with or without systemic lupus erythematosus (SLE). Major subtypes include acute CLE (ACLE), subacute CLE (SCLE), and chronic CLE (CCLE; e.g., discoid lupus erythematosus, DLE). Pathogenesis…
Erythema multiforme (EM) is an acute, immune-mediated eruption characterized by target lesions, commonly triggered by herpes simplex virus (HSV). Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe, life-threatening mucocutaneous reactions—usually drug-induced—marked by epidermal necrosis and detachment. EM is…
Urticaria (hives) consists of transient, pruritic wheals with or without angioedema due to mast cell activation and histamine release. It is classified by duration into acute (<6 weeks) and chronic (≥6 weeks), and by triggers into spontaneous and inducible (physical)…
