Dermatology

Atopic eczema is a chronic, relapsing, intensely itchy inflammatory skin disorder in which epidermal barrier dysfunction and immune dysregulation reinforce each other; management combines daily skin care, prompt anti-inflammatory treatment, infection recognition and escalation according to severity and life impact.

Benign skin lesions are common non-malignant growths such as seborrhoeic keratoses, epidermoid cysts, dermatofibromas, skin tags, lipomas and naevi; the high-yield skill is recognising reassuring patterns while identifying the changing, symptomatic or atypical lesion that needs specialist assessment or biopsy.

Contact dermatitis is eczema caused by an external contactant: irritant disease is dose-dependent barrier injury, whereas allergic disease is a delayed T-cell-mediated reaction in a sensitised person.

Erythema nodosum is a tender septal panniculitis and reaction pattern, usually presenting with bilateral shin nodules that fade like bruises; the key task is identifying an infectious, inflammatory, drug-related, pregnancy-related or other trigger.

Dermatophyte fungi digest keratin in the stratum corneum and spread outward as they consume it, producing a scaly lesion with an actively advancing, inflamed edge and a clearing centre, the ring that gives ringworm its name.

Impetigo is a contagious superficial bacterial skin infection, usually caused by Staphylococcus aureus or Streptococcus pyogenes, presenting as non-bullous crusted erosions or bullous flaccid blisters.

A leg ulcer is a wound below the knee that fails to heal, and its cause must be established before treatment: venous, arterial, diabetic/neuropathic, pressure, inflammatory, traumatic and malignant ulcers need different pathways.

Lichen planus is an inflammatory interface dermatosis causing pruritic violaceous papules with Wickham striae and potentially persistent disease of the mouth, genitals, scalp or nails.

Melanoma is malignant melanocytic disease requiring rapid specialist assessment, histological staging and stage-directed treatment; a changing pigmented lesion should not be reassured by a single visual rule.

Bacteria spreading along fascial planes thrombose the vessels supplying the overlying tissue, so fat and fascia die while the skin above can still look nearly normal.

Non-melanoma skin cancer mainly comprises basal cell carcinoma and cutaneous squamous cell carcinoma; distinguish their behaviour, refer appropriately and treat histologically confirmed disease according to site and risk.

Localised damage to skin and underlying tissue, usually over a bony prominence, caused by sustained pressure or pressure combined with shear; early recognition and pressure relief are the core interventions.

A chronic inflammatory facial dermatosis with flushing, persistent erythema, telangiectasia, papules or pustules, phymatous change and/or ocular disease; identify the dominant feature because treatment is feature-directed.

A contagious infestation by Sarcoptes scabiei causing intense nocturnal itch, burrows and a papular rash; cure requires correct whole-body treatment and simultaneous treatment of relevant close contacts.

A life-threatening severe cutaneous adverse reaction with painful epidermal necrosis or detachment and prominent mucosal disease; treat it as a skin-failure emergency until specialist assessment excludes it.

Mast-cell mediator release causes short-lived, itchy, blanching weals; histaminergic angioedema and anaphylaxis can accompany urticaria, while isolated angioedema may instead be bradykinin-mediated and needs a different pathway.