AMC MCQ Dermatology High-Yield Topics for IMGs

Last reviewed: May 2026 | Written by the MplusX Editorial Team

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An asymptomatic 54-year-old construction worker presents with a dark, asymmetric 7mm mole on his upper back.

He wants it checked. You suspect a melanoma.

Do you perform a punch biopsy, or a complete excision?

In Australia, skin cancer detection and the management of inflammatory dermatoses are core primary care responsibilities. The AMC MCQ heavily tests your diagnostic safety margins—and selecting the wrong biopsy method is an immediate fail-point.

You must be able to confidently manage pigmented skin lesions, differentiate severe drug reactions, and prescribe topical steroid potencies safely. Reading about AMC MCQ final revision plan might also be helpful.

This guide outlines the exact clinical pathways, biopsy rules, and drug eruption matrices you need to master for the exam.

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1. High-Yield Drug Eruptions Reference Matrix

Severe cutaneous adverse reactions (SCARs) are life-threatening, drug-induced conditions that require immediate recognition, drug cessation, and supportive care. The AMC MCQ tests your ability to differentiate these rashes based on systemic symptoms, mucosal involvement, and clinical timelines.

Memorize this comparison matrix:

Condition	Typical Onset Timeline	Key Cutaneous Features	Mucosal Involvement	Systemic & Laboratory Findings	Common Causative Drugs	Clinical Management
Stevens-Johnson Syndrome (SJS)	4 to 28 days after starting drug	<10% skin detachment (epidermal necrolysis). Atypical targetoid macules. Positive Nikolsky sign.	Severe (affecting >=2 mucosal sites: eyes, mouth, genitals)	Fever, severe pain, tachycardia.	Allopurinol, anticonvulsants (carbamazepine, phenytoin), sulfonamide antibiotics.	– Cease suspect drug. – Transfer immediately to ICU / Burns unit. – Aggressive fluid and supportive care.
Toxic Epidermal Necrolysis (TEN)	4 to 28 days after starting drug	>30% skin detachment (sheets of skin peeling off). Positive Nikolsky sign.	Severe and extensive (mucosal sloughing, severe pain, bleeding)	High fever, septic state, multi-organ failure.	Same high-risk drugs (Allopurinol, anticonvulsants, NSAIDs).	– Cease suspect drug. – Direct admission to ICU / Specialist Burns Unit. – Strict barrier nursing, fluid resuscitation, wound care.
DRESS Syndrome	2 to 8 weeks (delayed onset)	Morbilliform eruption, facial oedema, follicular pustules. No skin detachment.	Mild or absent mucosal involvement.	High fever, lymphadenopathy, eosinophilia, atypical lymphocytosis, hepatic impairment (hepatitis).	Anticonvulsants, allopurinol, sulfasalazine, minocycline.	– Cease suspect drug. – Systemic corticosteroids (prednisolone 0.5–1mg/kg). – Monitor liver and renal function closely.
AGEP (Acute Generalized Exanthematous Pustulosis)	1 to 2 days (rapid onset)	Dozens of small, non-follicular, sterile pustules on a background of edematous erythema, starting in flexures.	Minimal (<20% of cases, mild oral mucosal involvement)	High fever, marked neutrophilia.	Beta-lactam antibiotics (amoxicillin), macrolides, calcium channel blockers.	– Cease suspect drug. – Symptomatic treatment (moisturizers, topical steroids for itch). – Resolves spontaneously within 1–2 weeks with desquamation.

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2. Topical Corticosteroid Potency Matrix

A common error on the exam is prescribing a corticosteroid that is too potent for sensitive skin areas (like the face or flexures), causing skin atrophy, telangiectasia, and striae. Alternatively, prescribing a steroid that is too weak for thick plaque psoriasis on the elbows leads to treatment failure.

Ensure your prescribing knowledge aligns with these eTG potency classes:

Potency Class	Common Examples	First-Line Clinical Indications	Contraindicated / High-Risk Areas	Dosing Frequency & Duration
Mild	Hydrocortisone 0.5% – 1% (cream/ointment)	– Facial eczema / atopic dermatitis. – Flexural eczema (axillae, groin). – Infantile eczema.	N/A (Safe for sensitive skin)	Apply once or twice daily for up to 1 to 2 weeks during active flares.
Moderate	Clobetasone butyrate 0.05%	– Mild trunk/limb eczema. – Paediatric trunk eczema.	Avoid long-term use on the face.	Apply once or twice daily.
Potent	Betamethasone dipropionate 0.05% OR Methylprednisolone aceponate 0.1%	– Moderate to severe eczema on trunk/limbs. – Psoriasis. – Severe contact dermatitis.	Contraindicated on the face and flexures (causes rapid skin atrophy).	Apply once daily. Limit treatment duration to 2 to 4 weeks.
Very Potent	Clobetasol propionate 0.05%	– Resistant plaques of psoriasis. – Palmoplantar pustulosis. – Lichen sclerosus (genital).	Strictly contraindicated on the face. Limit total volume used to avoid systemic absorption.	Apply once daily. Restrict use to a maximum of 1 to 2 consecutive weeks.

Clinical Rule: In dermatology, ointments are preferred for dry, scaly, or hyperkeratotic lesions (as they are occlusive and increase drug penetration). Creams are reserved for moist, weeping, or intertriginous lesions.

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3. Melanoma: The Complete Excision Pathway

Melanoma is the third most common cancer in Australia. The AMC MCQ tests your diagnostic safety and procedural knowledge.

The ABCDE Criteria for Screening

* A – Asymmetry: One half of the lesion does not match the other. * B – Border Irregularity: Edges are ragged, notched, or blurred. * C – Colour Variation: Multiple shades of brown, black, blue, red, or white. * D – Diameter: Greater than 6mm (although melanomas can be smaller). * E – Evolving: Changing size, shape, colour, or presenting with new symptoms (bleeding, itching).

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The Excisional Biopsy Rule

If a lesion is clinically suspicious for melanoma, the correct next step is never a punch biopsy or shave biopsy. These partial biopsy techniques are clinical errors because they sample only a portion of the lesion, leading to: 1. Underestimation of the maximum Breslow thickness (which determines staging, prognosis, and wide local excision margins). 2. Potential tumor seeding or transection of the primary specimen.

The correct choice is a complete diagnostic excisional biopsy with 2mm lateral clinical margins and a deep cuff of subcutaneous fat.

Partial biopsies (incisional or punch) are only permitted if the lesion is exceptionally large, located in a cosmetically sensitive area (like the eyelid or nose), or if there is low clinical suspicion but biopsy is required to rule out pathology. These partial biopsies must be coordinated with a specialist dermatologist.

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4. Scabies Eradication: Australian Standards

Scabies, caused by the mite Sarcoptes scabiei, is characterized by intense, generalized pruritus (worse at night) and erythematous papules, burrows, and nodules in the web spaces, wrists, axillae, and genitalia.

The Eradication Protocol (eTG)

1. First-Line Agent: Permethrin 5% cream. 2. Administration Rules (highly tested): * Apply the cream to clean, dry skin from the neck down to the toes, ensuring complete coverage of the web spaces, under the nails, the umbilicus, and the cleft of the buttocks. * For children aged under 2 years, elderly patients, or immunocompromised individuals, the cream must also be applied to the face, ears, and scalp, avoiding only the eyes and mouth. * Leave the cream on the skin for 8 to 24 hours before washing off thoroughly with cool water. * Crucial Step: The application must be repeated exactly 7 days later to kill any newly hatched mites, as permethrin is not ovicidal. 3. Treat All Close Contacts: All household contacts and sexual partners must undergo treatment simultaneously, regardless of whether they have symptoms, to prevent re-infestation. 4. Environmental Cleaning: Wash all clothing, bedding, and towels used in the last 5 days in hot water (>60°C) and dry in a hot dryer. Items that cannot be washed must be sealed in a plastic bag for a minimum of 72 hours (which starves the mites to death).

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5. Inflammatory Dermatoses: Eczema, Psoriasis, and Acne Management

In addition to skin cancers and drug eruptions, the AMC MCQ heavily evaluates your clinical reasoning regarding standard GP skin clinics. You must master the step-wise, guideline-conforming management of three major inflammatory conditions: atopic dermatitis (eczema), plaque psoriasis, and acne vulgaris.

Atopic Dermatitis (Eczema): The Step-Up Protocol

Atopic dermatitis is characterized by dry, erythematous, pruritic skin flares. The Australian guideline (eTG) emphasizes a systematic approach:

1. Maintenance (The Foundation): Daily, liberal, and frequent application of non-perfumed emollients (moisturizers like QV cream, Cetaphil, or emulsifying ointment) to repair the skin barrier. Emollients should be continued even when skin is clear. Use soap-free washes. 2. Mild Flares: Apply a mild topical corticosteroid (hydrocortisone 1% cream/ointment) once or twice daily for up to 14 days. Safe for sensitive zones (face, flexures). 3. Moderate to Severe Flares: Step up to a potent topical corticosteroid (methylprednisolone aceponate 0.1% or betamethasone dipropionate 0.05%). Apply once daily to active lesions on the trunk and limbs. Limit treatment to 2 to 4 weeks. 4. Flexural or Facial Moderate Flares: If potent steroids are needed on the face or flexures (where steroid-induced atrophy happens rapidly), the guideline recommends topical calcineurin inhibitors, such as pimecrolimus 1% cream.

Plaque Psoriasis: First-line Management

Plaque psoriasis presents as well-demarcated, erythematous plaques with characteristic silvery-white scales, typically on extensor surfaces (elbows, knees, scalp). * First-line Topical Therapy: A combination of a potent topical corticosteroid with a vitamin D analogue: calcipotriol 50mcg/g + betamethasone dipropionate 500mcg/g (applied once daily for a maximum of 4 weeks). * Scale Reduction: For very thick scales, use a keratolytic agent such as salicylic acid 2% to 6% ointment prior to applying topical steroids to enhance penetration. * Systemic Referral: If the condition affects >10% of the body surface area, or is refractory to topical therapies, refer the patient to a dermatologist for phototherapy (narrowband UVB) or systemic agents (methotrexate, cyclosporine, or biologics).

Acne Vulgaris: Step-Wise Prescribing

Acne management is classified based on severity and the presence of inflammatory (papules, pustules) vs. non-inflammatory (comedones) lesions: Reading about MplusX review might also be helpful.

Key Prescribing Rules: * Oral Antibiotic Limit: When prescribing oral doxycycline for moderate acne, never use it as monotherapy (due to bacterial resistance). Always combine it with a topical retinoid or benzoyl peroxide. Limit the course of oral antibiotics to a maximum of 3 months. Reading about MplusX vs AMEDEX might also be helpful. * Isotretinoin Monitoring: Oral isotretinoin (Roaccutane) is highly teratogenic. In Australia, it must only be prescribed by a registered dermatologist. Female patients must participate in a pregnancy prevention program, use double contraception (e.g. COCP + barrier), and have monthly pregnancy tests. Monitor fasting lipids and liver function tests (LFTs) at baseline and during therapy.

Parasitic Infestations: Pediculosis Capitis (Head Lice)

A common pediatric dermatology presentation tested under Public Health is head lice. Differentiating the management of head lice from scabies is a high-yield exam skill: * First-line Non-Chemical Treatment: Physical removal (wet combing) using a fine-toothed head lice comb on hair coated with hair conditioner. This process must be repeated every 2 to 3 days for 14 days until no lice are found. * First-line Chemical Treatment: Apply a topical insecticide, such as permethrin 1% or malathion 0.5% liquid/cream, to dry hair from scalp to ends. Leave on for 10 minutes (permethrin) or 12 hours (malathion) before washing off. * The 7-Day Repeat Rule: Just like permethrin for scabies, chemical head lice treatments must be repeated exactly 7 days later to kill any newly hatched nymphs before they reach maturity. * School Exclusion Policy (Australian standard): Children do not need to be excluded from school or childcare, provided they are treated overnight and the treatment is commenced. They can return to school the morning after the first treatment.

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Frequently Asked Questions

What is the difference between SJS and TEN?

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis represent a spectrum of the same disease, classified solely by the percentage of body surface area (BSA) showing skin detachment (epidermal necrolysis): * SJS: <10% BSA skin detachment. * SJS/TEN Overlap: 10% to 30% BSA skin detachment. * TEN: >30% BSA skin detachment.

How do we manage post-scabies pruritus?

Following successful permethrin eradication, intense itching can persist for 2 to 4 weeks. This is a hypersensitivity reaction to dead mites and mite feces. It does not indicate treatment failure. Differentiate this on the exam: the correct management is symptomatic support with mild topical corticosteroids (hydrocortisone 1%) and oral antihistamines. Do not repeat permethrin treatment unless new burrows or active infestations are documented.

When should we perform a punch biopsy rather than an excisional biopsy?

A punch biopsy is indicated for diagnosing inflammatory dermatoses (like eczema, psoriasis, or vasculitis) or for evaluating suspected non-melanoma skin cancers (like basal cell carcinoma or squamous cell carcinoma) when the lesion is large and located in a site where complete excision would cause significant cosmetic or functional deformity before a definitive diagnosis is made.

What are the wide local excision (WLE) margins for melanoma?

Once a diagnostic excisional biopsy confirms melanoma, the patient must undergo a wide local excision. The margins are determined by the Breslow thickness reported on histopathology: * Melanoma In Situ: 5mm clinical margin. * Breslow Thickness <1.0mm: 10mm (1cm) clinical margin. * Breslow Thickness 1.0mm – 2.0mm: 10mm to 20mm clinical margin. * Breslow Thickness >2.0mm: 20mm (2cm) clinical margin.

What is the first-line treatment for mild to moderate atopic eczema?

First-line therapy consists of daily, liberal application of non-perfumed emollients (moisturizers like QV cream or Cetaphil) to repair the skin barrier. For active inflammatory flares, apply topical corticosteroids of appropriate potency (e.g. mild hydrocortisone 1% for the face; moderate clobetasone for limbs in children; potent methylprednisolone for limbs in adults) once or twice daily for up to 14 days.

How do we manage suspected squamous cell carcinoma (SCC)?

Unlike suspected melanoma (which requires immediate excision), suspected cutaneous SCC can be managed with either a diagnostic punch biopsy or a primary excisional biopsy with 4mm to 6mm clinical margins, depending on the size and location of the lesion. If the SCC is high-risk (diameter >20mm, located on the lip/ear, or in an immunocompromised patient), refer for specialist surgical excision or radiotherapy.

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Written by the MplusX Editorial Team — dedicated to providing clinically accurate, structured, and practical resources for international medical graduates pursuing licensing with the Australian Medical Council.

References

• John Murtagh‘s General Practice (8th Edition): Chapter 111: A diagnostic and management approach to skin problems, Page 2859; Chapter 113: Common skin problems, Page 2912; Chapter 114: Acute skin eruptions, Page 2971
• RACGP Red Book (10th edition): Chapter 9.4: Skin cancer, Page 113
• Therapeutic Guidelines (eTG): Part 2 Dermatology: Chapter 24: Paediatric dermatology, Page 287

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Disclaimer: This article is written for AMC MCQ examination preparation and general informational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. Clinical decisions should always be based on individual patient assessment, current Australian Therapeutic Guidelines (eTG), and consultation with qualified healthcare professionals. MplusX is an exam preparation platform and is not a substitute for supervised clinical training.