Common warts are benign epidermal proliferations caused by cutaneous human papillomaviruses (HPV), most often types 1, 2, 4, 27, and 57. They present as hyperkeratotic papules with thrombosed capillaries (“black dots”). Many resolve spontaneously within 1–2 years, but persistence is…

Molluscum contagiosum (MC) is a common, self-limited poxvirus infection presenting as dome-shaped, umbilicated papules. It spreads via skin-to-skin contact, fomites, and autoinoculation. Disease is more frequent in children, sexually active adults (genital/perineal), swimmers/wrestlers, and the immunosuppressed (numerous, atypical, giant lesions).…

Onycholysis is distal separation of the nail plate from the nail bed, producing a white/opaque area that may accumulate secondary debris and pigment. It is a sign, not a diagnosis, with diverse causes including trauma/over-grooming, psoriasis, onychomycosis, contact irritants/allergens, photosensitizing…

Paronychia is inflammation of the periungual folds. Acute paronychia is a rapid-onset bacterial infection (usually Staphylococcus aureus; occasionally streptococci or oral anaerobes in nail-biters) presenting with painful erythema, swelling, and possible abscess. Chronic paronychia is a multifactorial irritant/allergic dermatitis of…

Nail psoriasis affects up to 50% of patients with cutaneous psoriasis and is a strong risk factor for psoriatic arthritis (PsA). Matrix involvement causes pitting, leukonychia, crumbling; nail bed involvement causes onycholysis, oil-drop (salmon) patches, and subungual hyperkeratosis. Disease impacts…

Onychomycosis is a fungal infection of the nail unit caused by dermatophytes (most commonly Trichophyton rubrum), yeasts, or non-dermatophyte molds, leading to onycholysis, subungual hyperkeratosis, discoloration, and nail dystrophy. It is a chronic condition with cosmetic and functional impact, and…

Telogen effluvium is a non-scarring diffuse hair shedding disorder caused by a shift of hair follicles from anagen to telogen, leading to increased daily shedding. It can be acute (≤6 months) or chronic (>6 months). Triggers include physiological/psychological stress, febrile…

Androgenetic alopecia is the most common non-scarring hair loss, characterized by progressive miniaturization of hair follicles in androgen-sensitive scalp regions. Men show bitemporal recession and vertex thinning (Hamilton–Norwood patterns); women show diffuse central thinning with preserved frontal hairline (Ludwig/Sinclair patterns).…

Alopecia areata is a non-scarring, autoimmune hair loss disorder characterized by sudden, well-circumscribed patches of hair loss that can progress to total scalp (AT) or universal body hair loss (AU). Breakdown of hair follicle immune privilege with IFN-γ and JAK-STAT…

Post-inflammatory hyperpigmentation is an acquired hypermelanosis that follows cutaneous inflammation or injury. It is highly prevalent in skin of color (Fitzpatrick IV–VI) and can be epidermal, dermal, or mixed. PIH significantly impacts quality of life. Management prioritizes prevention (rapid control…