Skin Diseases

Disease / Phenomenon

Skin diseases encompass the conditions affecting the body's largest organ, which serves simultaneously as a physical barrier, immune sentinel, thermoregulator, sensory surface, and site of vitamin D synthesis. The category is broad: inflammatory conditions such as atopic dermatitis, psoriasis, acne, and rosacea; autoimmune disorders including vitiligo and pemphigus; infections; and malignancies from basal cell carcinoma to melanoma. Because the skin is visible, these conditions carry psychological and social weight disproportionate to their physical severity, and they frequently signal internal disease — metabolic, hepatic, endocrine, or autoimmune — making dermatologic examination a window onto systemic health. Prevalence is high and rising in industrialized populations.

Most inflammatory skin disease involves interaction between barrier function and immune activation. The stratum corneum depends on filaggrin, ceramides, and tight junctions; when these are compromised, allergens and microbes penetrate and keratinocytes release TSLP, IL-33, and IL-25. Atopic dermatitis follows a type 2 axis of IL-4, IL-13, and IL-31 with elevated IgE, whereas psoriasis is driven by the IL-23/Th17 axis with IL-17A and TNF-alpha producing keratinocyte hyperproliferation. Acne involves sebaceous activity, follicular hyperkeratinization, Cutibacterium acnes, and inflammasome activation. Oxidative stress, ultraviolet damage, and microbiome balance modulate all of these. This page maps the processes, pathways, and biomarkers.