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Arab Board Dermatology Clinical study materials
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Arab Board Dermatology Clinical practice questions

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Question 1Clinical assessment and diagnostic reasoning in dermatology

A 34-year-old woman has a well-demarcated erythematous plaque on the cheek with fine silvery scale that spares the nasolabial fold. Which single clinical feature most strongly supports a diagnosis of discoid lupus erythematosus over plaque psoriasis?

  1. Presence of Auspitz sign on gentle scraping
  2. Follicular plugging with scarring and atrophy Correct answer.
  3. Uniform silvery scale over the whole plaque
  4. Symmetry across extensor surfaces of elbows

Explanation

Discoid lupus erythematosus characteristically produces follicular plugging, adherent scale and eventual scarring with atrophy, features reflecting the interface dermatitis and follicular involvement. Psoriasis shows parakeratosis without scarring and classically yields pinpoint bleeding when scale is removed.

Question 2Clinical assessment and diagnostic reasoning in dermatology

Which finding on the soles of a patient with suspected palmoplantar psoriasis most reliably favours psoriasis over tinea pedis?

  1. Sharply marginated erythema with a collarette of scale Correct answer.
  2. Positive potassium hydroxide microscopy
  3. Advancing scaly border with central clearing
  4. Itching that worsens in warm weather

Explanation

Palmoplantar psoriasis produces well-demarcated erythema, often with a collarette of scale and sterile pustules, whereas dermatophyte infection typically shows an advancing annular border with central clearing. Mycological examination is the decisive test when the clinical picture is ambiguous.

Question 3Clinical assessment and diagnostic reasoning in dermatology

A patient reports recurrent crops of painful grouped vesicles on an erythematous base recurring at the same site on the buttock. Which diagnostic step is most appropriate to confirm the clinical impression?

  1. Wood lamp examination of the lesion
  2. Tzanck smear of a fresh vesicle base Correct answer.
  3. Patch testing with standard series
  4. Skin biopsy for direct immunofluorescence

Explanation

Recurrent grouped vesicles at a fixed site suggest herpes simplex, and a Tzanck smear from the base of a fresh vesicle demonstrates multinucleated giant cells with marginated chromatin. Direct immunofluorescence is reserved for suspected autoimmune blistering disease.

Question 4Clinical assessment and diagnostic reasoning in dermatology

Which clinical clue best distinguishes atopic dermatitis from seborrhoeic dermatitis in an adult?

  1. Involvement of the central face and presternal area
  2. Improvement with topical antifungal therapy
  3. Greasy yellow scale along the scalp margin
  4. Flexural lichenification with a personal history of asthma Correct answer.

Explanation

Atopic dermatitis in adults favours flexures with lichenification and is associated with atopy including asthma and allergic rhinitis. Seborrhoeic dermatitis shows greasy yellow scale in sebaceous-rich areas such as the scalp margin, central face and presternum.

Question 5Clinical assessment and diagnostic reasoning in dermatology

A 62-year-old man presents with a pearly papule on the lower eyelid with telangiectasia and a rolled border. Which diagnosis is most likely?

  1. Sebaceous hyperplasia
  2. Nodular basal cell carcinoma Correct answer.
  3. Squamous cell carcinoma
  4. Amelanotic melanoma

Explanation

A pearly papule with arborising telangiectasia and a rolled edge on a sun-exposed site such as the lower eyelid is the classic description of nodular basal cell carcinoma. Squamous cell carcinoma is typically hyperkeratotic and ulcerated rather than pearly.

Question 6Clinical assessment and diagnostic reasoning in dermatology

Which dermoscopic feature most strongly supports a diagnosis of pigmented basal cell carcinoma?

  1. Milky-red globules in the centre
  2. Branched streaks at the periphery
  3. Large blue-grey ovoid nests Correct answer.
  4. Regular pigment network throughout

Explanation

Large blue-grey ovoid nests and arborising vessels are dermoscopic hallmarks of pigmented basal cell carcinoma. A regular pigment network suggests a benign melanocytic lesion, and milky-red globules are not a recognised BCC criterion.

Question 7Clinical assessment and diagnostic reasoning in dermatology

A 28-year-old woman has a single annular scaly plaque on the trunk with central clearing and an active raised border. Which bedside test most directly supports the diagnosis?

  1. Skin scrapings for bacterial culture
  2. Wood lamp examination of the plaque
  3. Tzanck smear from the border
  4. KOH microscopy of scale from the active border Correct answer.

Explanation

An annular plaque with central clearing and an active scaly border suggests tinea corporis, and potassium hydroxide microscopy of scale taken from the advancing edge demonstrates septate hyphae. Sampling the central cleared area reduces yield.

Question 8Clinical assessment and diagnostic reasoning in dermatology

Which clinical feature is most characteristic of pityriasis rosea?

  1. Palmar desquamation with pastia lines
  2. Herald patch followed by a truncal Christmas-tree eruption Correct answer.
  3. Grouped vesicles along a dermatome
  4. Annular plaques with a collarette of scale on the face

Explanation

Pityriasis rosea typically begins with a herald patch followed by oval truncal lesions aligned along the ribs in a Christmas-tree distribution with a collarette of scale. Dermatomal vesicles indicate herpes zoster rather than pityriasis rosea.

Question 9Clinical assessment and diagnostic reasoning in dermatology

A patient has a chronic pruritic eruption on the wrists and forearms with small tense vesicles and a history of similar episodes after handling cement. Which diagnosis is most likely?

  1. Allergic contact dermatitis Correct answer.
  2. Miliaria crystallina
  3. Atopic dermatitis
  4. Dyshidrotic eczema

Explanation

Vesicular dermatitis confined to sites of contact with a known sensitiser such as cement, with a history of recurrence on re-exposure, is characteristic of allergic contact dermatitis. Patch testing confirms the responsible allergen.

Question 10Clinical assessment and diagnostic reasoning in dermatology

Which finding on examination best distinguishes erythroderma caused by psoriasis from that caused by eczema?

  1. Chronic pruritus with excoriations
  2. Diffuse fine scaling with flexural sparing
  3. Generalised lichenification with exudation
  4. Well-demarcated underlying plaques with nail pitting Correct answer.

Explanation

In psoriatic erythroderma the underlying plaques often remain sharply demarcated, and nail changes such as pitting or onycholysis support the diagnosis. Eczematous erythroderma tends to be poorly demarcated with lichenification and exudation.

Question 11Clinical assessment and diagnostic reasoning in dermatology

A child has honey-coloured crusted lesions around the nose and mouth. Which organism is the most likely cause?

  1. Corynebacterium minutissimum
  2. Streptococcus pyogenes
  3. Staphylococcus aureus Correct answer.
  4. Pseudomonas aeruginosa

Explanation

Non-bullous impetigo with honey-coloured crusts is most commonly caused by Staphylococcus aureus, with Streptococcus pyogenes also implicated. Corynebacterium minutissimum causes erythrasma, and Pseudomonas causes characteristic green-blue pus.

Question 12Clinical assessment and diagnostic reasoning in dermatology

Which clinical sign is most suggestive of scabies rather than eczema in an itchy child?

  1. Circinate plaques on the trunk
  2. Greasy scale on the scalp
  3. Dennie-Morgan infraorbital folds
  4. Burrows in the finger web spaces with nocturnal itch Correct answer.

Explanation

Linear burrows in the web spaces with intense nocturnal pruritus and often a household history are classic for scabies. Dennie-Morgan folds and flexural involvement favour atopic dermatitis.

Question 13Clinical assessment and diagnostic reasoning in dermatology

A 45-year-old woman has violaceous, pruritic, flat-topped papules on the flexor wrists with white lacy networks on the buccal mucosa. Which diagnosis is most likely?

  1. Lichen simplex chronicus
  2. Lichen planus Correct answer.
  3. Psoriasis
  4. Discoid lupus erythematosus

Explanation

The combination of violaceous flat-topped papules on flexor wrists with Wickham striae on the oral mucosa is diagnostic of lichen planus. Psoriasis would show silvery scale and extensor involvement without lacy oral lesions.

Question 14Clinical assessment and diagnostic reasoning in dermatology

Which feature of a pigmented lesion most raises concern for melanoma on clinical examination?

  1. Symmetric shape present since childhood
  2. Uniform brown colour with a regular border
  3. Diameter of 3 mm with a stable appearance
  4. Recent change in size, shape and colour with border irregularity Correct answer.

Explanation

The ABCDE criteria emphasise that recent evolution, border irregularity and colour variegation in a pigmented lesion raise suspicion for melanoma. Stability and symmetry since childhood favour a benign naevus.

Question 15Clinical assessment and diagnostic reasoning in dermatology

A patient with a chronic leg ulcer has an ulcer with a rolled, everted edge and a violaceous border. Which diagnosis should be considered first?

  1. Squamous cell carcinoma arising in a chronic ulcer Correct answer.
  2. Neuropathic diabetic ulcer
  3. Venous stasis ulcer
  4. Arterial ischaemic ulcer

Explanation

A rolled, everted edge with a violaceous rim in a chronic ulcer raises suspicion of malignant transformation, particularly squamous cell carcinoma in a Marjolin ulcer. Biopsy is required to confirm malignancy.

Question 16Clinical assessment and diagnostic reasoning in dermatology

Which clinical feature best distinguishes bullous pemphigoid from pemphigus vulgaris at the bedside?

  1. Flaccid blisters with mucosal erosions
  2. Tense intact blisters on an urticarial base Correct answer.
  3. Fragile blisters that rupture easily
  4. Positive Nikolsky sign on normal skin

Explanation

Bullous pemphigoid produces subepidermal blisters that are tense and often arise on an urticarial base, whereas pemphigus vulgaris causes intraepidermal acantholysis with flaccid blisters and prominent mucosal involvement.

Question 17Clinical assessment and diagnostic reasoning in dermatology

A 55-year-old man has a slowly enlarging, firm, skin-coloured nodule on the sun-exposed ear with overlying telangiectasia and a history of ulceration. Which diagnosis is most likely?

  1. Squamous cell carcinoma Correct answer.
  2. Actinic keratosis
  3. Nodular basal cell carcinoma
  4. Keratoacanthoma

Explanation

A firm, rapidly growing nodule on a sun-exposed ear that ulcerates and shows telangiectasia is highly suspicious for squamous cell carcinoma, which has a higher risk of metastasis on the ear and lip. Biopsy is required for confirmation.

Question 18Clinical assessment and diagnostic reasoning in dermatology

Which finding on examination favours a diagnosis of psoriasis over lichen simplex chronicus on the elbow?

  1. Improvement with emollients alone
  2. Sharply demarcated plaque with silvery micaceous scale Correct answer.
  3. History of atopy with flexural involvement
  4. Ill-defined area of lichenification with exaggerated skin markings

Explanation

Psoriasis produces sharply demarcated plaques with silvery micaceous scale, whereas lichen simplex chronicus shows ill-defined lichenification with exaggerated skin markings due to chronic rubbing.

Question 19Clinical assessment and diagnostic reasoning in dermatology

A neonate has a large, well-defined salmon-coloured macule on the nape of the neck that has been present since birth. Which is the most likely diagnosis?

  1. Port-wine stain
  2. Infantile haemangioma
  3. Congenital melanocytic naevus
  4. Naevus simplex Correct answer.

Explanation

A salmon-coloured, blanching macular lesion present at birth on the nape, glabella or eyelids is a naevus simplex (salmon patch), which tends to fade over time. Port-wine stains are darker, do not fade, and grow proportionally with the child.

Question 20Clinical assessment and diagnostic reasoning in dermatology

A young woman has recurrent painful genital ulcers with a history of similar oral ulcers. Which finding most supports Behçet disease?

  1. Pathergy reaction at a needle puncture site Correct answer.
  2. Positive Tzanck smear from the ulcer
  3. Culture positive for Haemophilus ducreyi
  4. Positive KOH from the ulcer base

Explanation

Behçet disease is supported by a positive pathergy reaction, an exaggerated inflammatory response to needle puncture, in the context of recurrent oral and genital ulceration. Tzanck smear and KOH address herpes and fungal infection respectively.

Question 21Clinical assessment and diagnostic reasoning in dermatology

Which clinical feature best distinguishes hidradenitis suppurativa from recurrent furunculosis?

  1. Double-ended comedones with sinus tracts in intertriginous skin Correct answer.
  2. Positive bacterial culture from pus
  3. Single large abscess with surrounding cellulitis
  4. Rapid response to a single antibiotic course

Explanation

Hidradenitis suppurativa is characterised by double-ended comedones, sinus tracts, scarring and nodules in intertriginous areas such as the axillae and groins. Furunculosis produces individual abscesses without comedones or sinus tracts.

Question 22Clinical assessment and diagnostic reasoning in dermatology

A 30-year-old woman has a malar erythema that spares the nasolabial folds and photosensitivity. Which laboratory test most directly supports systemic lupus erythematosus?

  1. Anti-desmoglein 3 antibody
  2. Serum tryptase level
  3. Serum complement C3 alone
  4. Antinuclear antibody titre Correct answer.

Explanation

A positive antinuclear antibody is the most sensitive screening test for systemic lupus erythematosus, and further specific antibodies such as anti-dsDNA support the diagnosis. Anti-desmoglein 3 is used for pemphigus vulgaris.

Question 23Clinical assessment and diagnostic reasoning in dermatology

Which feature on examination most suggests a diagnosis of acanthosis nigricans rather than post-inflammatory hyperpigmentation?

  1. Sharply demarcated hyperpigmented patch on the shin
  2. Pigmentation following a linear scratch
  3. Brown macular pigmentation at the site of a healed lesion
  4. Velvety brown thickening in the axillae and neck folds Correct answer.

Explanation

Acanthosis nigricans presents as velvety, thickened brown plaques in intertriginous areas such as the axillae and neck, often associated with insulin resistance. Post-inflammatory hyperpigmentation follows a healed inflammatory lesion in its original location.

Question 24Clinical assessment and diagnostic reasoning in dermatology

A patient has a tense, weeping, erythematous eruption confined to the area where a topical neomycin preparation was applied. Which diagnosis is most likely?

  1. Allergic contact dermatitis to the topical agent Correct answer.
  2. Secondary bacterial infection
  3. Nummular eczema
  4. Irritant contact dermatitis from occlusion

Explanation

A weeping eczematous eruption confined precisely to the area of application of a topical agent, especially an aminoglycoside antibiotic, suggests allergic contact dermatitis. Patch testing to the suspected agent confirms the diagnosis.

Question 25Clinical assessment and diagnostic reasoning in dermatology

Which clinical finding in a patient with a leg ulcer most favours a venous rather than arterial aetiology?

  1. Absent posterior tibial pulses
  2. Lipodermatosclerosis with haemosiderin staining Correct answer.
  3. Pain relieved by dependency
  4. Punched-out ulcer with a pale base

Explanation

Venous ulcers arise in the gaiter area with surrounding haemosiderin deposition, lipodermatosclerosis and oedema, reflecting chronic venous hypertension. Arterial ulcers are punched-out with a pale base and occur with absent pulses and pain relieved by dependency.

Question 26Clinical assessment and diagnostic reasoning in dermatology

A patient is being assessed for possible Raynaud phenomenon. Which finding on examination best supports a diagnosis of primary rather than secondary Raynaud phenomenon?

  1. Unilateral involvement of a single digit with a sharply demarcated border
  2. Symmetrical attacks affecting all fingers of both hands with sparing of the thumbs Correct answer.
  3. Attacks beginning after the age of 40 years with associated skin tightening
  4. Digital ulceration with pitting scars over the fingertips

Explanation

Primary Raynaud phenomenon is characteristically symmetrical, bilateral, affects the fingers (often sparing the thumbs) and lacks tissue damage or an underlying connective tissue disease. Asymmetry, ulceration, later onset and skin tightening all point to a secondary cause requiring further work-up.

Question 27Clinical assessment and diagnostic reasoning in dermatology

A patient has an intensely itchy eruption and the clinician suspects scabies. Which bedside examination technique most directly demonstrates the mite or its products?

  1. Using a Wood's lamp to look for coral-red fluorescence
  2. Applying firm pressure to a lesion to assess for blanching
  3. Performing diascopy with a glass slide over an erythematous patch
  4. Scraping the burrow with mineral oil and examining the material under light microscopy Correct answer.

Explanation

Microscopic examination of material scraped from a burrow, ideally with mineral oil, allows direct visualisation of mites, eggs or faecal pellets and is the standard confirmatory bedside test. The other techniques assess vascular or pigmentary characteristics and do not detect the mite.

Question 28Clinical assessment and diagnostic reasoning in dermatology

A patient with a long-standing, poorly controlled atopic dermatitis develops widespread coalescing lesions. Which clinical finding most suggests secondary bacterial infection rather than a flare of the underlying eczema?

  1. Lichenified plaques with exaggerated skin markings
  2. Excoriated papules confined to the antecubital fossae
  3. Generalised dryness with fine white scaling
  4. Honey-coloured crusting with a sudden worsening and fever Correct answer.

Explanation

Honey-coloured crusting, rapid deterioration and systemic features such as fever suggest bacterial superinfection, typically with Staphylococcus aureus, and warrant antimicrobial treatment. Dryness, lichenification and excoriations are features of chronic eczematous change rather than infection.

Question 29Clinical assessment and diagnostic reasoning in dermatology

A patient presents with a painful, unilateral vesicular eruption in a dermatomal distribution. Which finding on examination most increases the likelihood that the eruption is herpes zoster rather than a contact dermatitis?

  1. Grouped vesicles on an erythematous base that do not cross the midline Correct answer.
  2. Linear vesicles along the line of a scratch
  3. Weeping oedematous plaques with a sharp border at the site of a topical agent
  4. Poorly defined erythema with vesicles confined to areas of contact

Explanation

Herpes zoster produces grouped vesicles on an erythematous base in a dermatomal distribution that respects the midline, reflecting involvement of a single dorsal root ganglion. Contact dermatitis follows the pattern of exposure and is not confined by the midline.

Question 30Clinical assessment and diagnostic reasoning in dermatology

A patient has a lesion on the lower lip. Which clinical finding most strongly raises concern for squamous cell carcinoma rather than a benign chronic cheilitis?

  1. Diffuse dryness with scaling affecting both lips symmetrically
  2. Superficial fissuring at the commissures with maceration
  3. Recurrent crusting that resolves with emollient use
  4. An indurated, ulcerated plaque with an everted edge and fixation to underlying tissue Correct answer.

Explanation

Induration, ulceration, an everted edge and fixation to deeper tissue are features of an invasive malignant process and require biopsy. Symmetrical dryness, commissural fissuring and crusting that responds to emollients suggest benign inflammatory cheilitis.

Question 31Papulosquamous and eczematous disorders

A 24-year-old man has well-demarcated erythematous plaques with silvery scale on both elbows and knees, and pitting of several fingernails. Which diagnosis is most likely?

  1. Atopic dermatitis
  2. Pityriasis rosea
  3. Plaque psoriasis Correct answer.
  4. Lichen planus

Explanation

Extensor-surface plaques with silvery scale plus nail pitting are classic for plaque psoriasis, which is driven by keratinocyte hyperproliferation and inflammation. The distribution and nail findings distinguish it from flexural eczemas and from the violaceous, flexural, mucosal-predominant lichen planus.

Question 32Papulosquamous and eczematous disorders

Which finding on histology is most characteristic of lichen planus?

  1. Subcorneal pustules with eosinophils
  2. A band-like lymphocytic infiltrate at the dermoepidermal junction Correct answer.
  3. Parakeratosis with neutrophils in the stratum corneum
  4. Marked spongiosis with intraepidermal vesicles

Explanation

Lichen planus shows a lichenoid interface dermatitis with a dense band-like lymphocytic infiltrate hugging the dermoepidermal junction, with basal cell damage and saw-tooth rete ridges. This pattern reflects a T-cell-mediated attack on basal keratinocytes.

Question 33Papulosquamous and eczematous disorders

A 30-year-old woman has an oval, scaly, salmon-colored patch on the trunk followed a week later by many smaller similar lesions arranged along skin tension lines. What is the most likely diagnosis?

  1. Secondary syphilis
  2. Tinea corporis
  3. Pityriasis rosea Correct answer.
  4. Guttate psoriasis

Explanation

A herald patch followed by a truncal eruption distributed in a Christmas-tree pattern along cleavage lines is the classic presentation of pityriasis rosea. The eruption is usually self-limited and resolves over weeks to months.

Question 34Papulosquamous and eczematous disorders

Which feature best distinguishes seborrheic dermatitis from psoriasis of the scalp?

  1. Involvement of the scalp
  2. Chronic relapsing course
  3. Presence of fine scale
  4. Yellowish greasy scale with a less sharply demarcated border Correct answer.

Explanation

Seborrheic dermatitis typically shows yellowish, greasy scale on an ill-defined erythematous base, often involving the nasolabial folds and eyebrows. Psoriasis scale is silvery and the plaques are more sharply demarcated and thicker.

Question 35Papulosquamous and eczematous disorders

A 6-year-old child has intensely pruritic, ill-defined erythematous patches in the antecubital and popliteal fossae with lichenification. Which diagnosis is most likely?

  1. Atopic dermatitis Correct answer.
  2. Pityriasis rubra pilaris
  3. Psoriasis vulgaris
  4. Lichen simplex chronicus

Explanation

Pruritic, flexural, lichenified dermatitis in a child is characteristic of atopic dermatitis, driven by barrier dysfunction and type 2 inflammation. Flexural involvement and intense itch are key discriminators.

Question 36Papulosquamous and eczematous disorders

Which topical agent is considered first-line anti-inflammatory therapy for mild to moderate plaque psoriasis limited to a small body surface area?

  1. Topical corticosteroid Correct answer.
  2. Topical antibiotic
  3. Topical calcineurin inhibitor
  4. Topical antifungal

Explanation

Topical corticosteroids are first-line for limited plaque psoriasis because they reduce inflammation and keratinocyte proliferation. Potency is chosen according to body site and disease severity.

Question 37Papulosquamous and eczematous disorders

A 45-year-old with psoriasis has 3% body surface area involvement of the elbows and knees despite adequate topical therapy. Which next step is most appropriate?

  1. Add phototherapy or a systemic agent after reassessing disease burden Correct answer.
  2. Reassure and stop all treatment
  3. Escalate to potent topical corticosteroid under occlusion only
  4. Start a systemic biologic immediately

Explanation

When limited disease fails adequate topical therapy, options include narrowband UVB phototherapy or a systemic agent, chosen after reassessing severity and comorbidities. Phototherapy is a reasonable next step for moderate disease.

Question 38Papulosquamous and eczematous disorders

A 28-year-old woman with psoriasis is being considered for methotrexate. Which baseline assessment is most important before starting therapy?

  1. Serum calcium
  2. Serum ferritin
  3. Thyroid function tests
  4. Liver function tests and hepatitis serology Correct answer.

Explanation

Methotrexate is hepatotoxic and requires baseline liver enzymes and hepatitis B and C screening, along with renal function and blood counts. Regular monitoring continues during therapy.

Question 39Papulosquamous and eczematous disorders

Which clinical clue most strongly suggests a drug eruption rather than idiopathic pityriasis rosea?

  1. A herald patch preceding the eruption
  2. Mild pruritus
  3. Distribution along skin cleavage lines
  4. Recent initiation of a new medication with a widespread morbilliform eruption Correct answer.

Explanation

A temporal relationship with a newly started drug and a widespread morbilliform pattern favor a drug eruption, which can mimic pityriasis rosea. A herald patch and cleavage-line distribution instead support idiopathic pityriasis rosea.

Question 40Papulosquamous and eczematous disorders

Which pathogenetic mechanism best explains the development of guttate psoriasis after streptococcal pharyngitis?

  1. IgE-mediated mast cell degranulation
  2. Direct bacterial invasion of the epidermis
  3. Complement-mediated keratinocyte lysis
  4. Superantigen-driven T-cell activation Correct answer.

Explanation

Guttate psoriasis is triggered by streptococcal superantigens that activate T cells and drive a Th17-mediated inflammatory cascade in the skin. This immune activation produces the characteristic drop-like plaques.

Question 41Papulosquamous and eczematous disorders

A 50-year-old man has well-demarcated erythematous plaques in the axillae and groin with minimal scale and a glazed appearance. Which form of psoriasis is most likely?

  1. Pustular psoriasis
  2. Inverse psoriasis Correct answer.
  3. Erythrodermic psoriasis
  4. Guttate psoriasis

Explanation

Inverse psoriasis affects intertriginous areas where moisture and friction reduce scale, producing smooth, glazed erythematous plaques. It is often misdiagnosed as candidiasis or seborrheic dermatitis.

Question 42Papulosquamous and eczematous disorders

Which feature best supports a diagnosis of lichen planus over a lichenoid drug eruption?

  1. Widespread symmetric distribution
  2. Onset after starting a new medication
  3. Presence of Wickham striae and mucosal involvement Correct answer.
  4. Eosinophils on histology

Explanation

Wickham striae on the surface of violaceous, flat-topped papules and mucosal involvement are classic for idiopathic lichen planus. Lichenoid drug eruptions tend to be more widespread and lack these typical features.

Question 43Papulosquamous and eczematous disorders

A patient with lichen planus has painful erosive lesions of the oral mucosa. Which treatment is most appropriate first-line?

  1. Topical antifungal
  2. Oral antibiotic
  3. Topical corticosteroid Correct answer.
  4. Topical retinoid

Explanation

Topical corticosteroids are first-line for symptomatic oral lichen planus, especially erosive disease. Intralesional or systemic corticosteroids may be needed for refractory cases.

Question 44Papulosquamous and eczematous disorders

Which finding on histology most strongly supports psoriasis over chronic eczema?

  1. Subcorneal pustules with eosinophils
  2. Regular acanthosis with thinned suprapapillary plates and parakeratosis Correct answer.
  3. Spongiosis with intraepidermal vesicles
  4. Band-like lymphocytic infiltrate at the dermoepidermal junction

Explanation

Psoriasis shows regular acanthosis, thinning of suprapapillary plates, parakeratosis, and dilated capillaries in the papillary dermis. These features reflect accelerated keratinocyte turnover.

Question 45Papulosquamous and eczematous disorders

A 62-year-old with chronic plaque psoriasis develops erythroderma with fever, tachycardia, and widespread scaling. Which immediate concern is most important?

  1. Isolated nail dystrophy
  2. Seasonal allergic rhinitis
  3. Localized bacterial cellulitis
  4. Fluid and electrolyte imbalance with thermoregulatory failure Correct answer.

Explanation

Erythroderma impairs the skin barrier, leading to massive transepidermal water loss, electrolyte derangement, and thermoregulatory failure. These systemic complications require urgent supportive management.

Question 46Papulosquamous and eczematous disorders

Which factor most strongly predisposes to the development of seborrheic dermatitis?

  1. Malassezia colonization with an inflammatory response Correct answer.
  2. High dietary calcium intake
  3. Iron deficiency anemia
  4. Chronic sun exposure

Explanation

Seborrheic dermatitis is associated with Malassezia yeast colonization and the host inflammatory response to it, which is why antifungal therapy is effective. It is also more common in immunosuppressed individuals.

Question 47Papulosquamous and eczematous disorders

A 40-year-old with severe psoriasis is started on a TNF inhibitor. Which monitoring consideration is most important before initiation?

  1. Check serum amylase
  2. Measure 24-hour urine calcium
  3. Obtain a baseline audiogram
  4. Screen for latent tuberculosis infection Correct answer.

Explanation

TNF inhibitors impair granuloma formation and increase the risk of reactivating latent tuberculosis, so screening is mandatory before starting therapy. Other baseline evaluations address blood counts and liver function.

Question 48Papulosquamous and eczematous disorders

A 35-year-old with psoriasis develops new-onset arthritis of the distal interphalangeal joints with nail pitting and dactylitis. Which diagnosis is most likely?

  1. Gout
  2. Rheumatoid arthritis
  3. Osteoarthritis
  4. Psoriatic arthritis Correct answer.

Explanation

Psoriatic arthritis commonly involves the distal interphalangeal joints, is associated with nail changes, and can produce dactylitis. It is seronegative and often follows or accompanies skin disease.

Question 49Papulosquamous and eczematous disorders

A patient with known psoriasis develops sudden generalized erythema with sterile pustules at the margins of the erythema, fever, and leukocytosis after abrupt withdrawal of systemic corticosteroids. Which diagnosis is most likely?

  1. Erythema multiforme major
  2. Generalized pustular psoriasis Correct answer.
  3. Acute generalized exanthematous pustulosis
  4. Staphylococcal scalded skin syndrome

Explanation

Abrupt corticosteroid withdrawal is a well-recognized trigger for generalized pustular psoriasis, which presents with fever, leukocytosis, and sterile pustules on erythematous skin. It is a dermatologic emergency requiring urgent systemic therapy.

Question 50Papulosquamous and eczematous disorders

A 55-year-old with longstanding psoriasis on long-term potent topical corticosteroids develops thin, atrophic plaques with telangiectasia at the application sites. What is the most appropriate management?

  1. Continue the same regimen indefinitely
  2. Increase the potency of the corticosteroid
  3. Taper and rotate to a steroid-sparing agent Correct answer.
  4. Add an occlusive dressing over the steroid

Explanation

Topical corticosteroid atrophy results from prolonged use of potent agents; management involves tapering the steroid and switching to steroid-sparing therapy such as a vitamin D analogue or calcineurin inhibitor. Continued potent use would worsen atrophy.