Dermatology Revision: Medicine (Final MB) Lecture Report
Revision 2 (Final MB)
24 Minutes
200+ Candidates
Dermatology
1. Session Overview & Core Advice
This high-tempo revision masterclass provided final-year medical students with a laser-focused survey of examinable dermatology topics for the Final MB;BS examination. The lecturer reviewed the foundational structure and function of the skin, common inflammatory dermatoses, blistering disorders, and drug eruptions.
The Lecturer's Core Message: The examination tests classroom teaching, outpatient clinic attendance, and bedside recognition. Many dermatological morphological features cannot be appreciated solely through lecture notes. Students who grasp the high-yield rules, histological differentials, and exceptions highlighted in this session are well equipped to achieve maximum marks.
2. Systematic Topic Breakdown
Skin Embryology & Epidermal Layers
Epidermis is derived from embryonic ectoderm, whereas the dermis originates from mesoderm.
The epidermal layers (from deep to superficial) are: basale, spinosum, granulosum, lucidum, corneum. The stratum lucidum is absent in thin skin and found only in the palms and soles.
Eczema & Acne Vulgaris
Eczema: Hallmark histology is spongiosis (intercellular edema of the epidermis) with lymphocytic infiltration.
Acne Vulgaris: Pleomorphic eruption involving Cutibacterium acnes, sebum hypersecretion, and follicular hyperkeratinization.Examiner Note: Keloid is a secondary complication, NOT a morphological lesion type of acne.
Papulosquamous: Psoriasis vs. Lichen Planus
Both demonstrate the Koebner isomorphic phenomenon.
Psoriasis histology shows parakeratosis and Munro microabscesses. In contrast, Lichen Planus shows a dense band-like lymphocytic infiltrate at the dermo-epidermal junction and absence of microabscesses.Vitiligo is autoimmune but is NOT part of the papulosquamous family.
Stevens-Johnson Syndrome (SJS)
Major severe cutaneous adverse reaction. Common triggers: cotrimoxazole, antiepileptics, allopurinol, NSAIDs (chloroquine is documented but rare).
SCORTEN prognostic determinants: Advanced age, hematological/visceral malignancy, elevated serum urea, and hyperglycemia.
Pigmentary Conditions: Vitiligo vs. Albinism
Both are depigmenting disorders. Always describe pale skin as depigmented, never as hyperpigmented.
Vitiligo management: topical steroids and PUVA phototherapy. Albinism: lifelong broad-spectrum sunscreen and UV counseling; high lifetime risk of cutaneous Squamous Cell Carcinoma (SCC).
Bullous Cleavage Planes & Infections
Subepidermal cleavage: Bullous pemphigoid (tense blisters).
Intraepidermal cleavage: Pemphigus vulgaris (flaccid blisters, desmogleins 1 & 3).
Infections: Scabies presents with intense nocturnal pruritus (Sarcoptes scabiei). Tinea capitis is a hallmark cause of non-scarring alopecia in children.
3. Distinguishing Clinical Features at a Glance
| Condition | Key Clinical Presentation | Histological Hallmark / Management Note |
|---|---|---|
| Psoriasis | Silvery micaceous scaly plaques; Koebner phenomenon | Parakeratosis & Munro microabscesses (neutrophilic collections). |
| Lichen Planus | The 5 P's (purple, pruritic, polygonal, planar papules) | Band-like infiltrate at dermo-epidermal junction; absence of microabscesses. |
| Eczema (Dermatitis) | Pruritic ill-defined erythema, weeping, lichenification | Epidermal spongiosis and cellular lymphocytic infiltrate. |
| Bullous Pemphigoid | Tense, non-fragile bullae in elderly patients | Subepidermal cleavage with autoantibodies against hemidesmosomes. |
| Pemphigus Vulgaris | Flaccid fragile blisters, erosions, oral involvement | Intraepidermal cleavage; targeting desmogleins 1 & 3 (acantholysis). |
| Scabies | Severe nocturnal pruritus, burrows in web spaces | Sarcoptes scabiei; treat with 5% permethrin dermal cream. |
| Vitiligo / Albinism | Complete cutaneous depigmentation | PUVA phototherapy for vitiligo; rigorous photoprotection for albinism. |
4. Strategic Examination Advice
Picture / Spotter Stations: When presented with a clinical photograph, examine the morphological lesion carefully. Verify whether the area is depigmented orhyperpigmented before venturing a diagnostic label. Note anatomical distribution (flexor vs. extensor surfaces, photo-exposed areas).
Long Case Structure: Always present your case systematically: primary diagnosis, differential diagnoses, underlying pathophysiology, and a stepwise management plan (supportive care, topical therapy, systemic agents, and follow-up).
Scope of Revision: Working-level medical officer competency is the benchmark. Candidates do not need specialist dermatopathological arcana; focus on broad familiarity across the common clinical conditions covered in this report.