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Iran Specialty Board Dermatology study materials
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Iran Specialty Board Dermatology practice questions

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Question 1Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which epidermal layer contains cells that are actively dividing and attached to the basement membrane?

  1. Stratum basale Correct answer.
  2. Stratum granulosum
  3. Stratum spinosum
  4. Stratum corneum

Explanation

The stratum basale is a single layer of columnar keratinocytes resting on the basement membrane; these cells are the principal proliferative population of the epidermis and give rise to the layers above. Cells in the higher layers have already left the cell cycle and are committed to terminal differentiation.

Question 2Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Desmosomes in the epidermis derive their adhesive strength mainly from which interaction?

  1. Cadherins of adjacent cells binding in the extracellular space and linking to intermediate filaments Correct answer.
  2. Gap junctions allowing passage of small molecules between cells
  3. Integrins binding laminin in the basement membrane
  4. Selectins mediating leukocyte rolling on endothelium

Explanation

Desmosomes are formed by desmosomal cadherins (desmogleins and desmocollins) whose extracellular domains bind those of the opposing cell, while their cytoplasmic tails anchor to desmoplakin and keratin intermediate filaments. This transmembrane linkage to the cytoskeleton is what gives the epidermis its mechanical resilience.

Question 3Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

A patient has fragile skin and blisters that separate within the lower epidermis after minor trauma, with acantholysis on histology. Which protein is most likely defective?

  1. Collagen VII
  2. Keratin 5
  3. Desmoglein 1 Correct answer.
  4. Laminin 332

Explanation

Intraepidermal blistering with acantholysis reflects loss of desmosomal adhesion, classically from autoantibodies or mutations affecting desmogleins. Desmoglein 1 defects produce superficial splitting, as seen in staphylococcal scalded skin syndrome and in pemphigus foliaceus.

Question 4Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Melanocytes transfer pigment to surrounding keratinocytes primarily by which mechanism?

  1. Phagocytosis of melanocyte dendrite tips by keratinocytes Correct answer.
  2. Simple diffusion of melanin monomers across the plasma membrane
  3. Transfer of melanosomes through gap junctions
  4. Exocytosis of melanin into the intercellular space

Explanation

Melanocytes extend dendrites that are engulfed by adjacent keratinocytes, which then internalize the melanosome-containing tips. This cytophagic transfer delivers pigment in a controlled manner and forms the epidermal melanin unit.

Question 5Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which cell type in the epidermis is the principal antigen-presenting cell for contact sensitization?

  1. Keratinocyte
  2. Merkel cell
  3. Langerhans cell Correct answer.
  4. Melanocyte

Explanation

Langerhans cells are epidermal dendritic cells that capture haptens, migrate to draining lymph nodes, and present antigen to naive T cells, initiating contact hypersensitivity. Their Birbeck granules and CD1a expression are characteristic markers.

Question 6Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which immunoglobulin class predominates in the dermal perivascular infiltrate of a delayed-type hypersensitivity reaction?

  1. IgE
  2. IgM
  3. IgG4 Correct answer.
  4. IgA

Explanation

Delayed-type hypersensitivity is a T-cell-mediated process, but when antibody is present in chronic lesions it is typically IgG, with IgG4 often seen in chronic inflammatory and fibrosing dermatoses. The question distinguishes the IgG subclass pattern from IgE-mediated immediate reactions.

Question 7Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

In the skin immune system, which cytokine is central to recruiting neutrophils in acute generalized pustular dermatoses?

  1. IL-13
  2. IL-17A Correct answer.
  3. IL-4
  4. IL-31

Explanation

IL-17A produced by Th17 cells and other innate lymphoid cells drives neutrophil recruitment through chemokines such as CXCL8 and granulocyte colony-stimulating factor. This pathway underlies pustular psoriasis and related neutrophilic dermatoses and is targeted by anti-IL-17 biologics.

Question 8Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

A child has recurrent staphylococcal skin abscesses and eczema-like lesions, with elevated IgE and reduced neutrophil oxidative burst. Which diagnosis best fits this combination?

  1. Hyper-IgE syndrome
  2. Chronic granulomatous disease Correct answer.
  3. Wiskott-Aldrich syndrome
  4. Ataxia-telangiectasia

Explanation

Chronic granulomatous disease results from defective NADPH oxidase and impaired respiratory burst, causing recurrent catalase-positive bacterial and fungal infections. The eczematous dermatitis and elevated IgE can mimic hyper-IgE syndrome, but the abnormal oxidative burst test is the discriminating feature.

Question 9Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which structural feature distinguishes eccrine from apocrine sweat glands on histology?

  1. Apocrine glands have a straight duct opening directly onto the skin surface
  2. Eccrine glands empty into hair follicles
  3. Eccrine glands have a coiled secretory portion opening directly onto the skin surface Correct answer.
  4. Apocrine glands lack myoepithelial cells

Explanation

Eccrine glands have a coiled secretory segment in the deep dermis and a duct that spirals to a surface pore. Apocrine glands, by contrast, open into the follicular infundibulum and are concentrated in axillae and anogenital skin.

Question 10Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

The outermost layer of the hair follicle that continues as the epidermis at the follicular orifice is which structure?

  1. Inner root sheath
  2. Glass membrane
  3. Outer root sheath Correct answer.
  4. Hair cuticle

Explanation

The outer root sheath is continuous with the epidermis and surrounds the follicle, forming the bulge region that houses epithelial stem cells. The inner root sheath lies deeper and is composed of cuticle, Huxley, and Henle layers.

Question 11Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which collagen type predominates in the papillary dermis and forms fine anchoring fibrils?

  1. Type IV
  2. Type VII
  3. Type III Correct answer.
  4. Type I

Explanation

The papillary dermis is rich in type III collagen, which forms thin, loosely arranged fibrils, while the reticular dermis is dominated by type I. Type IV is a basement membrane component and type VII forms anchoring fibrils.

Question 12Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Loss-of-function mutations in filaggrin most directly impair which epidermal function?

  1. Skin barrier formation Correct answer.
  2. Sweat production
  3. Melanin synthesis
  4. Collagen cross-linking

Explanation

Filaggrin aggregates keratin filaments and is degraded into natural moisturizing factor, so its deficiency impairs cornification and barrier function. This predisposes to ichthyosis vulgaris and atopic dermatitis.

Question 13Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

A patient with blistering after sun exposure has elevated urinary porphyrins and skin fragility. Which enzyme deficiency is most likely?

  1. Ferrochelatase
  2. Protoporphyrinogen oxidase
  3. Coproporphyrinogen oxidase
  4. Uroporphyrinogen decarboxylase Correct answer.

Explanation

Porphyria cutanea tarda results from deficient uroporphyrinogen decarboxylase, causing accumulation of uroporphyrin and heptacarboxyl porphyrins. These water-soluble porphyrins produce photosensitivity with blisters and fragility on sun-exposed skin.

Question 14Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Inheritance of X-linked recessive ichthyosis is explained by deficiency of which enzyme?

  1. Ceramide synthase
  2. Lipoxygenase
  3. Steroid sulfatase Correct answer.
  4. Transglutaminase 1

Explanation

X-linked recessive ichthyosis is caused by deletion or mutation of the STS gene encoding steroid sulfatase, leading to accumulation of cholesterol sulfate and impaired desquamation. The condition affects males and produces polygonal dark scales.

Question 15Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which genetic mechanism best explains the segmental distribution of lesions in a patient with a mosaic RAS mutation?

  1. Uniparental disomy of the entire chromosome
  2. Mitochondrial inheritance
  3. Postzygotic mutation producing two cell populations Correct answer.
  4. Germline mutation inherited from an affected parent

Explanation

Segmental or mosaic disorders arise from a somatic mutation occurring after fertilization, so mutant and normal cells coexist along lines of Blaschko. This explains the streaky or block-like distribution of lesions.

Question 16Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which organism is the most common cause of erysipelas?

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

Explanation

Erysipelas is a superficial dermal and lymphatic infection most often caused by beta-hemolytic streptococci, especially Streptococcus pyogenes. The sharply demarcated, raised border reflects lymphatic involvement.

Question 17Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

A KOH preparation of a scaly lesion shows short hyphae and spores around hair shafts. Which organism is most consistent with this finding?

  1. Malassezia furfur Correct answer.
  2. Trichophyton rubrum
  3. Candida albicans
  4. Microsporum canis

Explanation

Malassezia furfur produces the spaghetti-and-meatballs appearance of short hyphae with clusters of spores, seen in pityriasis versicolor. It is a lipophilic yeast requiring lipid supplementation for culture.

Question 18Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which virus is most strongly associated with Merkel cell carcinoma?

  1. Epstein-Barr virus
  2. Merkel cell polyomavirus Correct answer.
  3. Human herpesvirus 8
  4. Human papillomavirus type 16

Explanation

Merkel cell polyomavirus is clonally integrated in most Merkel cell carcinomas, and its large T antigen contributes to oncogenesis. Detection of the virus supports the diagnosis in the appropriate histologic context.

Question 19Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Detection of which marker confirms that a spindle cell tumor in the dermis is of melanocytic origin?

  1. Desmin
  2. CD34
  3. S100 and Melan-A Correct answer.
  4. Cytokeratin

Explanation

Melanocytic tumors express S100, Melan-A, HMB-45, and SOX10, which together support melanocytic differentiation. S100 is sensitive but not entirely specific, so it is usually paired with Melan-A or SOX10.

Question 20Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which molecular pathway is most commonly activated by mutations in cutaneous melanoma?

  1. Notch pathway
  2. Wnt pathway via beta-catenin
  3. Hedgehog pathway via PTCH1
  4. MAPK pathway via BRAF V600E Correct answer.

Explanation

Activating BRAF V600E mutations occur in roughly half of melanomas and constitutively activate the MAPK cascade, promoting proliferation. This is the rationale for BRAF and MEK inhibitor therapy.

Question 21Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

A patient with basal cell carcinoma is treated with a Hedgehog pathway inhibitor. Which protein does vismodegib directly inhibit?

  1. SuFu
  2. GLI1
  3. SMO Correct answer.
  4. PTCH1

Explanation

Vismodegib inhibits smoothened (SMO), blocking Hedgehog signal transduction even when PTCH1 is lost. This suppresses downstream GLI activation and tumor growth in basal cell carcinoma.

Question 22Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which adhesion molecule is primarily responsible for keratinocyte attachment to the basement membrane at hemidesmosomes?

  1. E-cadherin
  2. CD44
  3. Desmoglein 3
  4. Alpha-6 beta-4 integrin Correct answer.

Explanation

Hemidesmosomes use alpha-6 beta-4 integrin to bind laminin 332 in the basement membrane, linking to keratin filaments through plectin and BPAG1. Disruption of this complex causes junctional epidermolysis bullosa or bullous pemphigoid.

Question 23Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which feature best distinguishes the dermal microvasculature of acral skin from that of the trunk?

  1. Glomus bodies and prominent arteriovenous anastomoses Correct answer.
  2. Absence of capillaries in the papillary dermis
  3. Lymphatic vessels opening directly onto the skin surface
  4. Presence of high endothelial venules throughout the dermis

Explanation

Acral skin contains numerous glomus bodies, which are specialized arteriovenous anastomoses that regulate temperature. These structures are concentrated in fingertips, toes, and nail beds.

Question 24Basic sciences relevant to skin (anatomy, histology, immunology, genetics, microbiology, molecular biology)

Which cell type is the primary source of type I collagen in the dermis?

  1. Fibroblast Correct answer.
  2. Mast cell
  3. Endothelial cell
  4. Langerhans cell

Explanation

Dermal fibroblasts synthesize and secrete procollagen, which is processed into mature type I collagen fibrils that provide tensile strength. Their activity is regulated by TGF-beta and mechanical tension.

Question 25Clinical dermatology: inflammatory and papulosquamous disorders

A 28-year-old man has well-demarcated erythematous plaques with silvery-white scale on both elbows and knees. Which histological finding most strongly supports psoriasis?

  1. Parakeratosis with regular acanthosis and thinning of the suprapapillary plates Correct answer.
  2. Compact orthokeratosis with a thickened granular layer
  3. Subcorneal pustules with acantholysis
  4. Interface dermatitis with vacuolar change at the dermoepidermal junction

Explanation

Psoriasis shows parakeratosis, regular (psoriasiform) acanthosis with clubbed rete ridges, thinning of suprapapillary plates, and dilated capillaries in the papillary dermis. Munro microabscesses may also be present. The other patterns point to different disease families.

Question 26Clinical dermatology: inflammatory and papulosquamous disorders

Which clinical sign refers to pinpoint bleeding when scale is removed from a psoriatic plaque?

  1. Nikolsky sign
  2. Auspitz sign Correct answer.
  3. Darier sign
  4. Koebner phenomenon

Explanation

The Auspitz sign is the appearance of small bleeding points after scale is scraped off, reflecting thinning of the suprapapillary epidermis over dilated dermal papillae. It is classically described in psoriasis.

Question 27Clinical dermatology: inflammatory and papulosquamous disorders

A patient with chronic plaque psoriasis has 18% body surface area involvement and no joint symptoms. According to typical severity classification, how is this best categorized?

  1. Moderate to severe psoriasis Correct answer.
  2. Psoriatic arthritis
  3. Mild psoriasis
  4. Localized palmoplantar psoriasis only

Explanation

Body surface area above 10% is generally classified as moderate-to-severe psoriasis, which supports consideration of systemic therapy or phototherapy. Involvement below 10% is usually regarded as mild.

Question 28Clinical dermatology: inflammatory and papulosquamous disorders

Which of the following is the most characteristic nail finding in psoriasis?

  1. Longitudinal melanonychia
  2. Koilonychia
  3. Pitting Correct answer.
  4. Onycholysis with a single large distal subungual mass

Explanation

Punctate nail pitting reflects focal parakeratosis of the nail matrix and is the most common and characteristic nail change in psoriasis. Oil-drop discoloration and onycholysis may also occur.

Question 29Clinical dermatology: inflammatory and papulosquamous disorders

A 34-year-old woman has pruritic, violaceous, flat-topped papules on the flexor wrists with fine white lines on the surface. What is the most likely diagnosis?

  1. Pityriasis rosea
  2. Psoriasis vulgaris
  3. Lichen planus Correct answer.
  4. Discoid eczema

Explanation

The six P's of lichen planus are pruritic, purple, polygonal, planar, papules, and plaques, often with Wickham striae and a predilection for flexural wrists. The violaceous color and white surface lines are distinctive.

Question 30Clinical dermatology: inflammatory and papulosquamous disorders

Which mucosal finding is most characteristic of oral lichen planus?

  1. Cobblestone plaques on the palate
  2. Punched-out ulcers with a yellow pseudomembrane
  3. Diffuse erythema with angular cheilitis
  4. Reticular white striae on the buccal mucosa Correct answer.

Explanation

Oral lichen planus most often presents as bilateral reticular white striae (Wickham striae) on the buccal mucosa. Erosive forms may occur but the reticular pattern is the classic sign.

Question 31Clinical dermatology: inflammatory and papulosquamous disorders

A 6-year-old child has multiple small scaly patches with loss of pigmentation on the cheek, and a Wood's lamp shows bright blue-white fluorescence. What is the diagnosis?

  1. Pityriasis alba Correct answer.
  2. Vitiligo
  3. Pityriasis versicolor
  4. Postinflammatory hypopigmentation

Explanation

Pityriasis alba is a common childhood hypopigmented, slightly scaly patch disorder that may show faint blue-white fluorescence on Wood's lamp examination. It is a mild form of eczema and usually self-limited.

Question 32Clinical dermatology: inflammatory and papulosquamous disorders

Which condition is characterized by a herald patch followed by oval truncal plaques with collarette scale along Langer lines?

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

Explanation

Pityriasis rosea classically begins with a herald patch, followed by oval salmon-colored plaques with collarette scale distributed along Langer cleavage lines on the trunk. It is usually self-limited.

Question 33Clinical dermatology: inflammatory and papulosquamous disorders

A 45-year-old woman has symmetric erythema and fine scale in the nasolabial folds, eyebrows, and presternal area. Which diagnosis is most likely?

  1. Atopic dermatitis
  2. Psoriasis vulgaris
  3. Rosacea
  4. Seborrheic dermatitis Correct answer.

Explanation

Seborrheic dermatitis favors sebaceous-rich areas such as the nasolabial folds, eyebrows, scalp, and presternal region, with greasy yellowish scale. Its distribution distinguishes it from psoriasis and atopic dermatitis.

Question 34Clinical dermatology: inflammatory and papulosquamous disorders

Which histologic feature is most characteristic of lichen planus?

  1. Psoriasiform hyperplasia with parakeratosis
  2. Subepidermal blister with linear IgA deposition
  3. Sawtooth rete ridges with a band-like lymphocytic infiltrate at the dermoepidermal junction Correct answer.
  4. Neutrophilic folliculitis with eosinophils

Explanation

Lichen planus shows hyperkeratosis, wedge-shaped hypergranulosis, sawtooth rete ridges, basal vacuolar degeneration, and a band-like lymphocytic infiltrate obscuring the dermoepidermal junction. Civatte bodies may be seen.

Question 35Clinical dermatology: inflammatory and papulosquamous disorders

A patient with psoriasis develops new plaques at sites of previous skin trauma. What is this phenomenon called?

  1. Isomorphic anergy
  2. Wolf isotopic response
  3. Koebner phenomenon Correct answer.
  4. Renbök phenomenon

Explanation

The Koebner phenomenon is the induction of typical lesions at sites of cutaneous injury and is well recognized in psoriasis, lichen planus, and vitiligo. It reflects an abnormal inflammatory response to trauma.

Question 36Clinical dermatology: inflammatory and papulosquamous disorders

Which biologic agent targets the p19 subunit shared by IL-23 and is used for moderate-to-severe plaque psoriasis?

  1. Secukinumab
  2. Guselkumab Correct answer.
  3. Etanercept
  4. Ustekinumab

Explanation

Guselkumab is a monoclonal antibody directed against the p19 subunit of IL-23, a key driver of the Th17 pathway in psoriasis. Ustekinumab targets the shared p40 subunit, while secukinumab targets IL-17A.

Question 37Clinical dermatology: inflammatory and papulosquamous disorders

A 30-year-old man has a generalized eruption of small drop-like scaly papules two weeks after a sore throat. Which trigger is most relevant?

  1. Recent vaccination
  2. Sun exposure
  3. Herpes simplex infection
  4. Streptococcal pharyngitis Correct answer.

Explanation

Guttate psoriasis classically erupts 1 to 3 weeks after group A streptococcal pharyngitis, especially in children and young adults. The drop-like papules favor the trunk and proximal extremities.

Question 38Clinical dermatology: inflammatory and papulosquamous disorders

Which form of psoriasis is a medical emergency characterized by generalized erythema and scaling with systemic toxicity?

  1. Erythrodermic psoriasis Correct answer.
  2. Scalp psoriasis
  3. Pustular psoriasis of the palms and soles
  4. Inverse psoriasis

Explanation

Erythrodermic psoriasis involves nearly the entire body surface with erythema and scaling and can cause fluid, electrolyte, and temperature dysregulation, making it a dermatologic emergency. Palmoplantar pustulosis and inverse psoriasis are localized forms.

Question 39Clinical dermatology: inflammatory and papulosquamous disorders

A patient with generalized pustular psoriasis has fever and widespread sterile pustules. Which genetic mutation is most strongly associated with this condition?

  1. FLG
  2. IL36RN Correct answer.
  3. ATP7B
  4. COL7A1

Explanation

Loss-of-function mutations in IL36RN, which encodes the IL-36 receptor antagonist, are associated with generalized pustular psoriasis. This leads to unchecked IL-36 signaling and neutrophilic inflammation.

Question 40Clinical dermatology: inflammatory and papulosquamous disorders

Which of the following best describes the typical distribution of inverse psoriasis?

  1. Smooth erythematous plaques in the axillae, inframammary folds, and groin Correct answer.
  2. Annular plaques with central clearing on the trunk
  3. Thick silvery plaques over the elbows and knees
  4. Punctate pits of the nail plate

Explanation

Inverse psoriasis affects intertriginous areas such as the axillae, groin, and inframammary folds, where maceration removes scale and leaves smooth, glistening erythematous plaques. It can be mistaken for candidiasis.

Question 41Clinical dermatology: inflammatory and papulosquamous disorders

Which first-line topical agent is appropriate for limited chronic plaque psoriasis?

  1. Oral methotrexate
  2. Systemic acitretin
  3. A potent topical corticosteroid Correct answer.
  4. Narrowband UVB phototherapy

Explanation

For limited plaque psoriasis, topical therapy with corticosteroids, vitamin D analogues, or combinations is first-line. Systemic agents and phototherapy are reserved for more extensive or refractory disease.

Question 42Clinical dermatology: inflammatory and papulosquamous disorders

A patient with psoriasis on methotrexate develops mouth ulcers, pancytopenia, and elevated transaminases. Which deficiency should be suspected?

  1. Vitamin C deficiency
  2. Vitamin B12 deficiency
  3. Folate deficiency Correct answer.
  4. Iron deficiency

Explanation

Methotrexate is a folate antagonist, and toxicity can cause mucositis, myelosuppression, and hepatotoxicity. Folinic acid rescue or folic acid supplementation is used to reduce these effects.

Question 43Clinical dermatology: inflammatory and papulosquamous disorders

Which feature distinguishes lichen planopilaris from typical lichen planus?

  1. Wickham striae on the buccal mucosa
  2. Pruritic annular plaques on the shins
  3. Violaceous papules on the wrists
  4. Scarring alopecia of the scalp Correct answer.

Explanation

Lichen planopilaris is a follicular variant of lichen planus that causes lymphocytic scarring alopecia, often with perifollicular erythema and scaling. The scarring nature distinguishes it from non-scarring alopecias.

Question 44Clinical dermatology: inflammatory and papulosquamous disorders

A 40-year-old woman has pruritic erythematous plaques with a fine white network on the buccal mucosa and a history of hepatitis C. Which condition is most strongly associated with hepatitis C?

  1. Pityriasis rosea
  2. Pityriasis alba
  3. Seborrheic dermatitis
  4. Lichen planus Correct answer.

Explanation

Hepatitis C infection is associated with lichen planus, and screening may be considered in affected patients. The mechanism is thought to involve immune dysregulation and viral antigen-driven T-cell responses.

Question 45Clinical dermatology: inflammatory and papulosquamous disorders

Which of the following is a recognized trigger for psoriasis exacerbation?

  1. Narrowband UVB phototherapy
  2. Beta-blocker therapy Correct answer.
  3. Regular emollient use
  4. Topical vitamin D analogue use

Explanation

Beta-blockers, lithium, antimalarials, and interferon can exacerbate psoriasis. Recognizing drug triggers is important because withdrawal of the offending agent may improve disease control.

Question 46Clinical dermatology: inflammatory and papulosquamous disorders

A patient with long-standing psoriasis develops dactylitis, enthesitis, and inflammatory back pain. What is the diagnosis?

  1. Erythrodermic psoriasis
  2. Psoriatic arthritis Correct answer.
  3. Palmoplantar pustulosis
  4. Generalized pustular psoriasis

Explanation

Psoriatic arthritis can present with peripheral arthritis, dactylitis, enthesitis, and axial involvement, and may occur in patients with skin psoriasis. Early recognition allows targeted therapy to prevent joint damage.

Question 47Clinical dermatology: inflammatory and papulosquamous disorders

A 25-year-old woman has a pruritic eruption with violaceous papules, Wickham striae, and a band-like infiltrate on biopsy. Which medication is most likely to induce this eruption?

  1. Metformin
  2. Acetaminophen
  3. Gold salts Correct answer.
  4. Penicillin

Explanation

Lichenoid drug eruptions can be induced by gold salts, antimalarials, thiazides, and captopril, among others. They clinically and histologically resemble lichen planus but may show eosinophils and parakeratosis.

Question 48Clinical dermatology: inflammatory and papulosquamous disorders

Which histologic clue most helps distinguish a lichenoid drug eruption from idiopathic lichen planus?

  1. Presence of eosinophils and parakeratosis Correct answer.
  2. Wedge-shaped hypergranulosis
  3. Sawtooth rete ridges
  4. Band-like lymphocytic infiltrate

Explanation

Lichenoid drug eruptions may show eosinophils, parakeratosis, and deeper infiltrates with less hypergranulosis, whereas idiopathic lichen planus typically has wedge-shaped hypergranulosis and sawtooth rete ridges. The distinction guides drug withdrawal.

Question 49Clinical dermatology: inflammatory and papulosquamous disorders

A patient with severe psoriasis on cyclosporine develops hypertension and rising creatinine. Which mechanism best explains cyclosporine nephrotoxicity?

  1. Crystal deposition in tubules
  2. Direct tubular epithelial necrosis
  3. Immune complex glomerulonephritis
  4. Afferent arteriolar vasoconstriction Correct answer.

Explanation

Cyclosporine causes dose-dependent nephrotoxicity mainly through afferent arteriolar vasoconstriction, reducing renal blood flow and glomerular filtration. Blood pressure and renal function require monitoring during therapy.

Question 50Clinical dermatology: inflammatory and papulosquamous disorders

A 28-year-old man has well-demarcated erythematous plaques with silvery scale on both elbows and knees. He also has pitting of several fingernails. Which nail finding is most strongly associated with this disorder?

  1. Longitudinal melanonychia of a single nail
  2. Oil-drop discoloration with onycholysis Correct answer.
  3. Transverse ridging following each febrile illness
  4. Painless subungual exostosis of the distal phalanx

Explanation

Nail involvement in psoriasis classically includes pitting, oil-drop (salmon) spots, and onycholysis, often with subungual hyperkeratosis. Oil-drop spots reflect focal parakeratosis and are highly suggestive when seen with skin plaques. Beau lines and single-nail melanonychia point to other diagnoses.