Definition Erythema Multiforme (EM): an acute, immune-mediated skin reaction characterized by target lesions. Often self-limiting but can be recurrent. Two main types: EM Minor: limited skin involvement, no mucosal lesions EM Major: mucosal involvement ± systemic symptoms; overlaps with Stevens-Johnson Syndrome Epidemiology & Risk Factors Peak incidence: young adults (20–40 years) Slight male predominance Common triggers: Infections (most common): HSV (herpes simplex virus), Mycoplasma pneumoniae Medications (less common): sulfonamides, NSAIDs, anticonvulsants Vaccinations or idiopathic Clinical Features Feature Description High-Yield Points Skin lesions Target (iris) lesions: concentric rings with central dusky area, raised border, erythematous halo Classic lesion = targetoid papule…
Author: Dr Ben
Definition Tinea infections (dermatophytoses): superficial fungal infections caused by Trichophyton, Microsporum, and Epidermophyton species. Classified by body site: Tinea capitis – scalp Tinea corporis – body (excluding scalp, groin, feet, nails) Tinea cruris – groin (“jock itch”) Epidemiology & Risk Factors Type Age/Population Risk Factors Tinea capitis Children 3–7 years Crowded settings, poor hygiene, close contact, African descent at higher risk Tinea corporis All ages Warm, humid climate, contact with infected person or animal Tinea cruris Adults, mostly males Obesity, sweating, tight clothing, diabetes, immunosuppression Clinical Features Feature Tinea Capitis Tinea Corporis Tinea Cruris Lesion Scaly patches, alopecia, broken hairs,…
Definition Impetigo: superficial bacterial skin infection, commonly affecting children. Characterized by pustules, vesicles, or honey-colored crusts, usually on the face or extremities. Highly contagious via direct contact or fomites. Epidemiology & Risk Factors Most common in children aged 2–5 years, but can occur at any age. More common in hot, humid climates. Risk factors: Minor skin trauma (scratches, insect bites) Pre-existing eczema or dermatitis Crowded living conditions Poor hygiene Etiology Staphylococcus aureus – most common cause Streptococcus pyogenes (Group A Streptococcus) Mixed infections possible Clinical Features Feature Description High-Yield Points Lesion type Vesicles, pustules, or bullae; ruptures to form honey-colored…
Definition Folliculitis: inflammation of the hair follicles, usually due to infection, irritation, or obstruction. Typically presents as small, erythematous papules or pustules centered on hair follicles. Epidemiology & Risk Factors Common in all age groups; more frequent in adults. Risk factors: Bacterial infection (most commonly Staphylococcus aureus) Occlusive clothing, friction, sweating Hot tubs or swimming pools (Pseudomonas aeruginosa) Immunosuppression or diabetes Clinical Features Feature Description High-Yield Points Lesions Small, erythematous papules or pustules Centered on hair follicle; may have hair in center Distribution Can occur anywhere with hair; commonly beard, scalp, chest, back, thighs Hot tub folliculitis: trunk and buttocks…
Overview Both acne vulgaris and rosacea are common facial skin conditions but have distinct etiologies, age groups, and treatments. Recognising differences is essential for diagnosis and PLAB-style vignettes. Comparison Table Feature Acne Vulgaris Rosacea Etiology Follicular hyperkeratinization + Propionibacterium acnes inflammation Chronic inflammatory disorder; dysregulation of innate immunity and vascular reactivity; triggers include UV, heat, alcohol, spicy food Age group Adolescents (12–25 years) Adults 30–50 years Distribution Face (T-zone), chest, back Central face: cheeks, nose, forehead, chin Lesion type Comedones (open/closed), papules, pustules, cysts Papules, pustules, erythema, telangiectasia; no comedones Triggers Hormonal changes, oily skin, cosmetics Sun, heat, alcohol, spicy…
Definition Molluscum contagiosum (MC): a benign, self-limiting viral skin infection caused by molluscum contagiosum virus (MCV), a poxvirus. Characterized by small, flesh-colored, dome-shaped papules with central umbilication. Epidemiology & Risk Factors Common in children aged 1–10 years, sexually active adults, and immunocompromised patients (e.g., HIV). Highly contagious via direct skin-to-skin contact or fomites (towels, clothing). Incubation period: 2–8 weeks. Clinical Features Feature Description High-Yield Points Lesions 2–5 mm, firm, dome-shaped, pearly/flesh-colored papules Central umbilication is characteristic Distribution Children: face, trunk, limbs; Adults: genital area (sexually transmitted) Linear arrangement may indicate autoinoculation Number Often multiple; may coalesce Can be a clue…
BCC vs SCC vs Melanoma Feature Basal Cell Carcinoma (BCC) Squamous Cell Carcinoma (SCC) Malignant Melanoma Origin Basal cells of epidermis Keratinocytes of epidermis Melanocytes Incidence Most common skin cancer Second most common Less common but most deadly Malignant Potential Rarely metastasizes Low–moderate metastatic risk High metastatic potential Growth Slow-growing, locally invasive Faster-growing, may invade locally Variable; often rapid vertical growth (nodular type) Common Sites Sun-exposed: nose, eyelids, cheeks Sun-exposed: face, ears, scalp, lips Men: back; Women: legs; face/arms also Appearance Pearly, translucent nodule; telangiectasia; central ulcer “rodent ulcer” Scaly, keratotic, firm nodule; may ulcerate; cutaneous horn Pigmented lesion; ABCDE:…
Definition Basal Cell Carcinoma (BCC): most common non-melanoma skin cancer, originating from basal cells of the epidermis. Rarely metastasizes but can cause local tissue destruction if untreated. Epidemiology & Risk Factors Most common in fair-skinned adults >50 years. Chronic UV exposure is the main risk factor. Other risk factors: Immunosuppression Previous radiotherapy Genetic syndromes (e.g., Gorlin syndrome) Clinical Features Feature Description High-Yield Points Appearance Pearly, translucent papule or nodule with telangiectasia Often slow-growing Ulceration Central ulcer (“rodent ulcer”) Common in neglected lesions Pigmentation Can be pigmented in darker skin May mimic melanoma Common sites Face (nose, eyelids), ears, neck Sun-exposed…
Definition Malignant melanoma: aggressive melanocyte-derived skin cancer with high potential for metastasis. Most serious form of skin cancer; early detection is crucial. Epidemiology & Risk Factors Accounts for ~1–2% of skin cancers but majority of skin cancer deaths. Peak incidence: 50–60 years. Risk factors: UV exposure (especially intermittent, severe sunburns in childhood) Fair skin, light hair, blue/green eyes Multiple or atypical nevi Family history of melanoma Immunosuppression Clinical Features ABCDE Criteria (high-yield for recognition) Letter Feature Significance A Asymmetry One half unlike the other B Border Irregular, notched, poorly defined C Colour Variegated (brown, black, red, white, blue) D Diameter…
Definition Seborrheic dermatitis (SD): chronic, relapsing, inflammatory skin condition affecting sebaceous-rich areas. Characterized by erythematous, greasy, yellowish scales. Often mildly pruritic, more common in infants and adults. Epidemiology & Risk Factors Affects 2–5% of adults, more in men. Peaks: infants (“cradle cap”) and adults 30–60 years. Risk factors: Neurological disorders (Parkinson’s disease) HIV infection Stress, cold weather Oily skin or seborrhea Pathophysiology Malassezia yeast overgrowth on sebaceous skin → inflammatory response. Genetic and immune factors contribute. Sebum production promotes yeast proliferation. Clinical Features Feature Typical Location Appearance Infants Scalp (“cradle cap”), face, diaper Yellow, greasy scales, minimal erythema Adults Scalp,…
Definition Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin condition associated with pruritus, dry skin, and eczema, often linked to atopy (asthma, allergic rhinitis). Epidemiology & Risk Factors Prevalence: 10–20% in children, 2–5% in adults. Most cases begin before age 5. Family history of atopy increases risk. Triggers: irritants (soap, detergents), allergens, stress, infections (Staphylococcus aureus). Pathophysiology Skin barrier dysfunction → increased transepidermal water loss. Immune dysregulation → Th2-dominant inflammation. Pruritus-scratch cycle → worsens lesions. Clinical Features Feature Children Adults Distribution Face, scalp, extensor surfaces Flexural areas (elbows, knees), hands, eyelids Appearance Red, weeping, crusted lesions Lichenified, dry plaques…
Definition Psoriasis: chronic, immune-mediated inflammatory skin disorder characterized by well-demarcated, erythematous plaques with silvery scales. Commonly involves extensor surfaces, scalp, and sacral region. Epidemiology & Risk Factors Prevalence: 2–3% worldwide. Can affect any age; peak onset: 20–30 and 50–60 years. Triggers: trauma (Koebner phenomenon), infection (streptococcal pharyngitis → guttate psoriasis), stress, drugs (β-blockers, lithium, antimalarials, NSAIDs). Genetic predisposition: HLA-Cw6 association. Types of Psoriasis Type Features Key Points Plaque (Psoriasis vulgaris) Most common, well-demarcated erythematous plaques with silvery scales Extensor surfaces, scalp Guttate Small drop-like lesions Often post-streptococcal; acute onset Inverse Smooth, red plaques in flexures Less scaling; intertriginous areas Pustular…