Papulosquamous Disorders Flashcards
Which of the following papulosquamous disorders is characterized by sharply demarcated, erythematous plaques with mica-like scale, predominantly affecting the elbows, knees, and scalp?
A) Lichen planus
B) Pityriasis rosea
C) Psoriasis
D) Dermatophytosis
Answer: C) Psoriasis
Rationale: Psoriasis presents with well-defined, erythematous plaques covered with silvery (mica-like) scale, commonly affecting extensor surfaces such as the elbows, knees, and scalp.
A 30-year-old woman presents with purple, polygonal papules associated with severe pruritus and lacy white markings. Which condition is most likely?
A) Psoriasis
B) Lichen planus
C) Pityriasis rosea
D) Dermatophytosis
Answer: B) Lichen planus
Rationale: Lichen planus is characterized by the “6 Ps”—pruritic, polygonal, planar, purple papules and plaques—often with lacy white markings (Wickham striae), particularly in mucosal involvement.
Which of the following conditions is commonly associated with a “herald patch” followed by oval plaques with a trailing scale in a “fir-tree” distribution?
A) Psoriasis
B) Lichen planus
C) Pityriasis rosea
D) Dermatophytosis
Answer: C) Pityriasis rosea
Rationale: Pityriasis rosea typically begins with a herald patch, followed by the eruption of multiple smaller lesions in a characteristic “fir-tree” distribution on the trunk.
A patient presents with sharply defined scaly plaques associated with hair loss. A KOH preparation reveals branching hyphae. What is the most likely diagnosis?
A) Psoriasis
B) Lichen planus
C) Pityriasis rosea
D) Dermatophytosis
Answer: D) Dermatophytosis
Rationale: Dermatophytosis (tinea) is a fungal infection that can cause scaly plaques with or without inflammation. A positive KOH test showing branching hyphae confirms the diagnosis.
Which histologic feature is most characteristic of psoriasis?
A) Interface dermatitis
B) Hyphae and neutrophils in the stratum corneum
C) Pathologic features often nonspecific
D) Acanthosis and vascular proliferation
Answer: D) Acanthosis and vascular proliferation
Rationale: Psoriasis is characterized histologically by acanthosis (epidermal hyperplasia) and vascular proliferation, which contribute to its thickened, scaly plaques.
What is the most common clinical variant of psoriasis?
A) Guttate psoriasis
B) Inverse psoriasis
C) Pustular psoriasis
D) Plaque psoriasis
Answer: D) Plaque psoriasis
Rationale: Plaque psoriasis is the most common form of psoriasis, characterized by stable, erythematous, well-demarcated plaques covered with silvery-white scale. It primarily affects the elbows, knees, gluteal cleft, and scalp.
Which of the following factors is most likely to trigger guttate psoriasis?
A) Emotional stress
B) β-Hemolytic streptococcal infection
C) Sun exposure
D) Metabolic syndrome
Answer: B) β-Hemolytic streptococcal infection
Rationale: Guttate psoriasis often follows a streptococcal throat infection, leading to the sudden appearance of numerous small, scaly papules. It is most common in children and young adults.
The Koebner phenomenon in psoriasis refers to:
A) Improvement of psoriatic plaques with UV exposure
B) Development of new psoriatic lesions at sites of skin trauma
C) Nail involvement with pitting and subungual hyperkeratosis
D) Increased cardiovascular risk in psoriasis patients
Answer: B) Development of new psoriatic lesions at sites of skin trauma
Rationale: The Koebner phenomenon describes the appearance of psoriasis in areas of skin trauma, such as scratches, burns, or surgical scars.
Which of the following medications is known to exacerbate psoriasis?
A) Antihistamines
B) Beta-blockers
C) Acetaminophen
D) Proton pump inhibitors
Answer: B) Beta-blockers
Rationale: Certain medications, including beta-blockers, lithium, and antimalarials, can worsen psoriasis or trigger flares.
Which of the following best describes the classic nail changes seen in psoriasis?
A) Longitudinal ridging and yellow discoloration
B) Pitting, onycholysis, and subungual hyperkeratosis
C) White nail beds with a red lunula
D) Clubbing and spoon-shaped nails
Answer: B) Pitting, onycholysis, and subungual hyperkeratosis
Rationale: Psoriatic nail changes include pitting (tiny depressions in the nail plate), onycholysis (separation of the nail from the nail bed), and subungual hyperkeratosis (thickening under the nail).
Psoriatic arthritis (PsA) most commonly presents as:
A) Symmetric polyarthritis resembling rheumatoid arthritis
B) Arthritis mutilans with severe joint destruction
C) Spondylitis with sacroiliac joint involvement
D) Distal arthritis with nail dystrophy
Answer: A) Symmetric polyarthritis resembling rheumatoid arthritis
Rationale: About 50% of PsA cases present as symmetric polyarthritis, which may mimic rheumatoid arthritis, but lacks rheumatoid factor positivity.
What is the first-line systemic treatment for generalized pustular psoriasis in nonpregnant patients?
A) Systemic corticosteroids
B) Oral retinoids
C) Methotrexate
D) Topical calcineurin inhibitors
Answer: B) Oral retinoids
Rationale: Oral retinoids (e.g., acitretin) are the first-line systemic therapy for generalized pustular psoriasis. Systemic corticosteroids should be avoided, as their withdrawal can trigger worsening disease.
Which form of psoriasis is most commonly found in intertriginous areas such as the axilla and groin?
A) Plaque psoriasis
B) Guttate psoriasis
C) Inverse psoriasis
D) Erythrodermic psoriasis
Answer: C) Inverse psoriasis
Rationale: Inverse psoriasis occurs in intertriginous areas (axilla, groin, submammary folds, and navel) and often presents without scale due to the moist environment.
What is the primary immunopathologic mechanism driving psoriasis?
A) Overproduction of histamine by mast cells
B) Excess melanocyte activation
C) T-cell mediated cytokine release leading to keratinocyte hyperproliferation
D) Autoantibody production against epidermal desmosomes
Answer: C) T-cell mediated cytokine release leading to keratinocyte hyperproliferation
Rationale: Psoriasis is an immune-mediated disease driven by T-cell activation, which leads to the release of proinflammatory cytokines (e.g., TNF-α, IL-17, IL-23), causing keratinocyte hyperproliferation.
Summary of Key Points Covered in the MCQs:
✅ Plaque psoriasis is the most common form
✅ Guttate psoriasis is triggered by streptococcal infection
✅ Koebner phenomenon describes trauma-induced lesions
✅ Beta-blockers and lithium can worsen psoriasis
✅ Psoriasis frequently affects nails (pitting, onycholysis, hyperkeratosis)
✅ Symmetric polyarthritis is the most common PsA subtype
✅ Oral retinoids are first-line for pustular psoriasis
✅ Inverse psoriasis affects intertriginous areas
✅ Psoriasis is an immune-mediated disease driven by T-cell cytokines
✅ Patients have an increased risk of metabolic syndrome and cardiovascular disease
Which topical agent is an alternative to glucocorticoids and is effective for treating mild to moderate psoriasis?
A) Salicylic acid
B) Calcipotriene
C) Cyclosporine
D) Hydroxychloroquine
Answer: B) Calcipotriene
Rationale: Calcipotriene, a vitamin D analogue, is effective for treating mild to moderate psoriasis. It regulates keratinocyte differentiation and proliferation, reducing plaque formation.
Why should systemic glucocorticoids be avoided in psoriasis treatment?
A) They are ineffective in treating psoriasis
B) They can cause life-threatening pustular psoriasis upon withdrawal
C) They significantly increase the risk of tuberculosis
D) They can cause Koebner phenomenon
Answer: B) They can cause life-threatening pustular psoriasis upon withdrawal
Rationale: Systemic glucocorticoids should not be used for psoriasis, as their withdrawal can trigger generalized pustular psoriasis, which can be life-threatening.
Which of the following is a major side effect of UV-light therapy for psoriasis?
A) Increased risk of skin cancer
B) Hypopigmentation of psoriatic plaques
C) Liver toxicity
D) Increased cardiovascular risk
Answer: A) Increased risk of skin cancer
Rationale: UV light therapy (including PUVA, narrowband UVB, and UVA) is effective for widespread psoriasis but can increase the risk of nonmelanoma and melanoma skin cancer.
Which of the following systemic agents is especially useful for psoriasis when immunosuppression must be avoided?
A) Methotrexate
B) Acitretin
C) Cyclosporine
D) TNF-α inhibitors
Answer: B) Acitretin
Rationale: Acitretin, a synthetic retinoid, is useful for psoriasis when immunosuppression must be avoided. However, it is teratogenic and should not be used in women planning pregnancy.
Apremilast, a phosphodiesterase-4 (PDE4) inhibitor, must be used cautiously in patients with:
A) Osteoporosis
B) Depression and renal failure
C) Diabetes mellitus
D) Hypertension
Answer: B) Depression and renal failure
Rationale: Apremilast is a PDE4 inhibitor approved for psoriasis and psoriatic arthritis. It should be used cautiously in patients with depression (due to reports of mood changes) and renal failure (due to altered drug clearance).
Which systemic psoriasis treatment is contraindicated in patients with congestive heart failure (CHF)?
A) Methotrexate
B) TNF-α inhibitors
C) Narrowband UVB therapy
D) Acitretin
Answer: B) TNF-α inhibitors
Rationale: TNF-α inhibitors (e.g., infliximab, etanercept) can worsen congestive heart failure and should be avoided in CHF patients.
What is the mechanism of action of methotrexate in the treatment of psoriasis?
A) TNF-α inhibition
B) Phosphodiesterase-4 inhibition
C) Inhibition of DNA synthesis by blocking dihydrofolate reductase
D) Retinoid receptor activation
Answer: C) Inhibition of DNA synthesis by blocking dihydrofolate reductase
Rationale: Methotrexate is a dihydrofolate reductase inhibitor, reducing DNA synthesis and T-cell activity, which helps control psoriasis and psoriatic arthritis.
Which of the following is a classic clinical feature of lichen planus (LP)?
A) Honey-colored crusting
B) Polygonal, pruritic, violaceous papules
C) Greasy scales over erythematous patches
D) Target lesions
Answer: B) Polygonal, pruritic, violaceous papules
Rationale: LP is characterized by the “6 Ps”—pruritic, polygonal, planar, purple, papules, and plaques. These lesions often exhibit Wickham’s striae (a network of gray-white lines on the surface).
Lichen planopilaris refers to LP affecting which anatomical site?
A) Nails
B) Oral mucosa
C) Scalp
D) Genitalia
Answer: C) Scalp
Rationale: Lichen planopilaris is LP of the scalp, which can lead to scarring alopecia if untreated.
Which of the following is a known trigger or association with lichen planus?
A) Epstein-Barr virus
B) Hepatitis C virus
C) Staphylococcus aureus
D) Human papillomavirus
Answer: B) Hepatitis C virus
Rationale: LP has been associated with hepatitis C infection, and patients with LP, especially oral LP, should be screened for HCV.
Which of the following drugs can cause a lichenoid drug eruption resembling lichen planus?
A) Acetaminophen
B) Thiazide diuretics
C) Metformin
D) Omeprazole
Answer: B) Thiazide diuretics
Rationale: Thiazide diuretics, gold, antimalarial agents, penicillamine, and phenothiazines can cause lichenoid drug eruptions mimicking LP
Which of the following is a hallmark feature of pityriasis rosea (PR)?
A) Herald patch
B) Wickham’s striae
C) Nikolsky’s sign
D) Gottron’s papules
Answer: A) Herald patch
Rationale: PR starts with a “herald patch” (a large annular lesion) followed by multiple smaller scaly lesions on the trunk, classically in a “Christmas tree” distribution.
How long does a typical episode of pityriasis rosea last?
A) 1–2 weeks
B) 3–8 weeks
C) 3–6 months
D) Over a year
Answer: B) 3–8 weeks
Rationale: PR is self-limiting and typically lasts 3–8 weeks. Treatment is symptomatic, focusing on pruritus relief with antihistamines or topical steroids.
What is the preferred management approach for mild cases of pityriasis rosea?
A) Systemic steroids
B) Narrowband UVB therapy
C) Symptomatic treatment with antihistamines and topical steroids
D) Oral acyclovir
Answer: C) Symptomatic treatment with antihistamines and topical steroids
Rationale: PR is self-limited, and treatment is directed at controlling pruritus using antihistamines and mid-potency topical glucocorticoids. UVB phototherapy may be useful in extensive cases.
