Master Specialist Dermatology (DER5421)
for DHA Speciality

Core Concepts

Dermatology involves the study of skin, hair, and nails. Key to diagnosis is understanding primary and secondary lesions, their morphology, configuration, and distribution. Primary lesions include macule, papule, plaque, nodule, vesicle, bulla, pustule, wheal. Secondary lesions result from primary lesion evolution or external factors, e.g., scale, crust, erosion, ulcer, fissure, atrophy, lichenification, scar. A strong grasp of skin anatomy (epidermis, dermis, subcutis) and basic pathophysiology (inflammation, infection, neoplasia, autoimmune processes) is crucial.

Clinical Presentation

• Inflammatory Dermatoses:
  • Psoriasis: Chronic, immune-mediated. Erythematous plaques with silvery scales, well-demarcated, extensor surfaces (elbows, knees), scalp, nails. Auspitz sign, Koebner phenomenon. Types: chronic plaque, guttate, inverse, pustular, erythrodermic.
  • Atopic Dermatitis (Eczema): Pruritic, chronic inflammatory skin condition. Erythema, papules, vesicles, oozing, crusting in acute phases; lichenification in chronic. Flexural areas in adults, face/extensors in infants. Often personal/family history of atopy.
  • Contact Dermatitis: Acute or chronic inflammation from irritant exposure or allergic sensitization. Well-demarcated erythema, vesicles, bullae, pruritus, in exposed areas.
  • Lichen Planus: "6 Ps" - Pruritic, Polygonal, Planar, Purple, Papules, Plaques. Wickham's striae (oral mucosa), can affect hair (scarring alopecia) and nails.
  • Urticaria (Hives): Transient (usually <24h), pruritic, erythematous, edematous wheals. May be acute or chronic, associated with angioedema.
• Infections:
  • Bacterial: Impetigo (honey-crusted erosions), Cellulitis (erythema, warmth, tenderness, poorly demarcated), Erysipelas (sharply demarcated, raised erythema). Folliculitis, furuncles, carbuncles.
  • Fungal (Tinea): Annular, scaly, pruritic plaques with central clearing (tinea corporis). Specific forms: tinea pedis, cruris, unguium, capitis. Candida presents with erythematous plaques, satellite papules/pustules in intertriginous areas.
  • Viral: Herpes Simplex (grouped vesicles on an erythematous base), Varicella/Zoster (dermatomal distribution of vesicles/crusts), Warts (verrucous papules, HPV), Molluscum Contagiosum (umbilicated papules).
• Autoimmune/Blistering:
  • Pemphigus Vulgaris: Flaccid bullae, erosions, positive Nikolsky sign, often oral involvement. Intraepidermal blistering.
  • Bullous Pemphigoid: Tense bullae on erythematous or normal skin, negative Nikolsky sign, often elderly patients. Subepidermal blistering.
  • Cutaneous Lupus Erythematosus: Malar rash ("butterfly rash"), discoid lesions (atrophic, scarred plaques with follicular plugging, scarring alopecia), photosensitivity.
• Neoplasms:
  • Basal Cell Carcinoma (BCC): Pearly papule/nodule with telangiectasias, rolled border, central ulceration. Most common skin cancer, rarely metastasizes.
  • Squamous Cell Carcinoma (SCC): Erythematous, scaly, crusted nodule or plaque, often ulcerated. Sun-exposed areas. Can metastasize. Keratoacanthoma is a variant.
  • Melanoma: High-risk. ABCDEs: Asymmetry, Border irregularity, Color variation, Diameter (>6mm), Evolving (change in size, shape, color, symptoms). Types: superficial spreading, nodular, lentigo maligna, acral lentiginous.
• Other Common: Acne Vulgaris, Rosacea, Seborrheic Dermatitis.

Diagnosis (Gold Standard)

Often clinical assessment is sufficient for many common conditions. However, definitive diagnosis for complex, atypical, or neoplastic lesions relies on:

• Biopsy (Histopathology): Punch, shave, or excisional biopsy for suspected neoplasms, blistering diseases, chronic inflammatory conditions, and any atypical or non-responsive dermatosis. Essential for defining diagnosis and guiding management.
• Direct Immunofluorescence (DIF): Perilesional skin biopsy for autoimmune blistering diseases (pemphigus, pemphigoid) and connective tissue diseases (lupus) to detect antibody deposition.
• Microbiological Tests:
  • KOH prep: Fungal elements for tinea/candida.
  • Tzank smear: Multinucleated giant cells for Herpesviridae infections.
  • Bacterial culture: For suspected bacterial infections.
• Patch Testing: Gold standard for diagnosing allergic contact dermatitis.
• Dermatoscopy: In-vivo examination of skin lesions, especially for pigmented lesions and early melanoma detection.
• Serology: Autoantibodies (ANA, anti-dsDNA, anti-Ro/La) for connective tissue diseases; specific autoantibodies for blistering diseases.

Management (First Line)

Management strategies depend heavily on the specific diagnosis and severity:

• Topical Corticosteroids: Mainstay for most inflammatory dermatoses (psoriasis, eczema, lichen planus). Potency varies based on site and severity.
• Emollients/Moisturizers: Essential for barrier repair in dry skin conditions like eczema, psoriasis, xerosis.
• Antihistamines: For symptomatic relief of pruritus (e.g., urticaria, eczema).
• Phototherapy (UVB/UVA): For extensive psoriasis, severe eczema, vitiligo, CTCL.
• Systemic Agents:
  • Immunosuppressants: Methotrexate, cyclosporine, azathioprine, mycophenolate for severe psoriasis, eczema, autoimmune blistering diseases, CTDs.
  • Biologics: For severe, recalcitrant psoriasis, atopic dermatitis, urticaria (e.g., TNF-α inhibitors, IL-17/23 inhibitors, IL-4/13 inhibitors).
  • Systemic Corticosteroids: For acute severe inflammatory conditions, blistering diseases, severe drug reactions (short-term).
• Anti-infectives: Appropriate topical/oral antifungals, antivirals (acyclovir), antibiotics based on culture/susceptibility.
• Surgery: Excisional biopsy for skin cancers (BCC, SCC, melanoma). Mohs micrographic surgery for high-risk BCC/SCC in cosmetically sensitive areas. Cryotherapy, electrodessication and curettage for benign lesions and some superficial cancers.
• Acne: Topical retinoids, benzoyl peroxide, topical/oral antibiotics, oral isotretinoin for severe nodulocystic acne.