Pathophysiology of Psoriasis — MCQs
Assertion: Vitamin D analogues are effective in psoriasis. Reason: They reduce keratinocyte proliferation
All are true about psoriasis except –
Which interleukin is specifically secreted by Th17 cells?
Psoriasis is exacerbated by -
"Isomorphic response" can be a feature of the following except
The burrow in scabies is in
Vitamin D analogues (such as calcitriol and calcipotriol) are useful in the treatment of:
A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?
A 16-year-old boy presented with asymptomatic, multiple erythematous annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. What is the most likely diagnosis?
Civatte bodies are a characteristic histological feature of which condition?
Pathophysiology of Psoriasis Indian Medical PG Practice Questions and MCQs
Question 1: Assertion: Vitamin D analogues are effective in psoriasis. Reason: They reduce keratinocyte proliferation
- A. Both A & R true, R explains A (Correct Answer)
- B. A false R true
- C. Both A & R true, R doesn't explain A
- D. A true R false
Explanation: ***Both A & R true, R explains A*** - **Vitamin D analogues** (e.g., calcipotriol) are a cornerstone treatment for psoriasis because they effectively modulate **keratinocyte proliferation** and differentiation. - Psoriasis is characterized by the **rapid overgrowth of keratinocytes**, and the antiproliferative effects of vitamin D analogues directly address this pathological hallmark. *A false R true* - This option is incorrect because both the assertion (Vitamin D analogues are effective in psoriasis) and the reason (They reduce keratinocyte proliferation) are individually true. - The effectiveness of vitamin D analogues in treating psoriasis is well-established in dermatological practice. *Both A & R true, R doesn't explain A* - This option is incorrect because the reduction of keratinocyte proliferation is precisely *how* vitamin D analogues exert their therapeutic effect in psoriasis. - The mechanism of action described in the reason directly explains the efficacy mentioned in the assertion. *A true R false* - This option is incorrect because the reason ("They reduce keratinocyte proliferation") is a fundamental and well-understood mechanism by which vitamin D analogues work in psoriasis. - Vitamin D analogues bind to vitamin D receptors in keratinocytes, influencing gene expression to inhibit their excessive growth.
Question 2: All are true about psoriasis except –
- A. Auspitz sign positive
- B. Parakeratosis & acanthosis
- C. Joint involvement in 5–10% (Correct Answer)
- D. Pitting of nails
- E. Koebner phenomenon
Explanation: ***Joint involvement in 5–10%*** - While **psoriasis** is a skin condition, it can involve the joints in about **30% of patients**, leading to **psoriatic arthritis**. - Therefore, stating that joint involvement occurs in only **5-10%** is incorrect, as the percentage is significantly higher. - This is the **FALSE statement** in this EXCEPT question. *Auspitz sign positive* - The **Auspitz sign** (pinpoint bleeding when scales are removed) is a classic feature of psoriasis. - It occurs due to the proximity of dilated capillaries to the thinned suprapapillary epidermis. - This is a **TRUE statement**. *Parakeratosis & acanthosis* - **Parakeratosis** (retention of nuclei in the stratum corneum) and **acanthosis** (epidermal hyperplasia) are classic histopathological features of psoriasis. - These features reflect the **rapid cell turnover** and **thickening of the epidermis** characteristic of psoriatic plaques. - This is a **TRUE statement**. *Pitting of nails* - **Nail pitting** is a common manifestation of psoriasis, affecting up to **50% of patients** with chronic plaque psoriasis and **80% of patients with psoriatic arthritis**. - Other nail changes include **onycholysis**, **subungual hyperkeratosis**, and discoloration. - This is a **TRUE statement**. *Koebner phenomenon* - **Koebner phenomenon** (isomorphic response) is the development of psoriatic lesions at sites of trauma or injury. - This is seen in approximately **25% of patients** with psoriasis and is a well-recognized clinical feature. - This is a **TRUE statement**.
Question 3: Which interleukin is specifically secreted by Th17 cells?
- A. IFN Gamma
- B. IL6
- C. IL-17 (Correct Answer)
- D. IL-22
Explanation: ***IL22*** - Th17 cells predominantly secrete **IL-17** and also produce **IL-22**, which is significant in mucosal immunity and inflammation [1]. - **IL-22** plays a crucial role in the response to infections and in the pathogenesis of inflammatory diseases. *IL16* - IL-16 is primarily associated with **chemoattractant and regulatory functions** for lymphocytes and not directly secreted by Th17 cells. - It is involved in **eosinophil and T cell activation**, which is not characteristic of the Th17 response. *IFN Gamma* - IFN-gamma is mainly produced by **Th1 cells** and is critical for **cell-mediated immunity**, which is distinct from the function of Th17 cells. - It plays a role in activating **macrophages**, unlike Th17 cells which focus on **neutrophil recruitment** and inflammation. *IL6* - While IL-6 is a pro-inflammatory cytokine that can be involved in various immune responses, it is not primarily secreted by Th17 cells. - It is produced by a variety of cell types including fibroblasts and macrophages, acting as a mediator in the **acute phase response**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 158-160.
Question 4: Psoriasis is exacerbated by -
- A. Beta-blockers
- B. Lithium
- C. Antimalarials
- D. All of the options (Correct Answer)
Explanation: ***All of the above*** - **Beta-blockers**, **lithium**, and **antimalarial drugs** are well-established medications that can exacerbate or trigger psoriasis flares. - Patients with psoriasis require careful monitoring when these medications are prescribed, with consideration of alternative treatments when feasible. ***Beta-blockers*** - **Non-selective beta-blockers** (particularly propranolol) can worsen existing psoriasis or induce new-onset disease. - The mechanism likely involves alterations in **T-cell function** and **epidermal proliferation**. - Risk is higher with non-selective agents compared to cardioselective beta-blockers. ***Lithium*** - **Lithium**, used for bipolar disorder, is a frequent and well-documented psoriasis trigger. - Can induce or worsen various forms including **plaque psoriasis**, **pustular psoriasis**, and **erythrodermic psoriasis**. - Exacerbations typically occur within weeks to months of initiation. ***Antimalarials*** - **Chloroquine** and **hydroxychloroquine** can precipitate severe psoriasis flares. - Particularly associated with **erythrodermic** and **generalized pustular psoriasis**. - Mechanism involves **immune cell activation** and amplification of inflammatory pathways.
Question 5: "Isomorphic response" can be a feature of the following except
- A. Tinea (Correct Answer)
- B. Warts
- C. Molluscum contagiosum
- D. Psoriasis
Explanation: ***Tinea*** - The **isomorphic response (Koebner phenomenon)** refers to the development of new skin lesions in areas of trauma due to an immunological process. - This phenomenon is **not typically seen in tinea** (fungal infections). - While tinea can spread to new areas, this occurs through **direct fungal inoculation and contact spread**, not through the true Koebner mechanism. *Warts* - **Warts** caused by human papillomavirus (HPV) can exhibit the **isomorphic response**. - Trauma to the skin can lead to **viral inoculation** in that area, resulting in new wart formation along lines of trauma. - This is a well-recognized example of Koebner phenomenon in viral infections. *Molluscum contagiosum* - **Molluscum contagiosum** (poxvirus infection) can demonstrate the **isomorphic response**. - **Scratching or rubbing** can spread the virus to new areas through autoinoculation. - New lesions develop along the lines of trauma, consistent with Koebner phenomenon. *Psoriasis* - **Psoriasis** is the **classic and most well-known** condition exhibiting the isomorphic response or Koebner phenomenon. - New psoriatic plaques appear in areas of **skin injury** (scratches, cuts, burns, surgical incisions, friction). - Seen in approximately **25-50%** of psoriasis patients.
Question 6: The burrow in scabies is in
- A. S. corneum (Correct Answer)
- B. Malpighian layer
- C. S. germinatum
- D. S. granulosum
Explanation: ***S. corneum*** - The **burrow** created by the *Sarcoptes scabiei* mite is specifically found within the **stratum corneum** of the epidermis. - This superficial location allows the mite to feed on **keratinocytes** and deposit eggs, leading to the characteristic rash and intense itching. - The burrow appears as a **serpiginous tract** and is a pathognomonic finding in scabies. *Malpighian layer* - The **Malpighian layer** encompasses the **stratum basale** and **stratum spinosum**, which are deeper layers of the epidermis. - The scabies mite does not burrow into these deeper, metabolically active layers. *S. germinatum* - **Stratum germinativum** is another term for the **stratum basale**, the deepest epidermal layer responsible for cell division. - The scabies mite creates burrows at a much more superficial level in the stratum corneum. *S. granulosum* - The **stratum granulosum** lies between the stratum spinosum and stratum corneum. - While closer to the surface than the Malpighian layer, scabies burrows are specifically located in the more superficial **stratum corneum**, not the granulosum layer.
Question 7: Vitamin D analogues (such as calcitriol and calcipotriol) are useful in the treatment of:
- A. Pemphigus
- B. Leprosy
- C. Psoriasis (Correct Answer)
- D. Lichen planus
Explanation: ***Psoriasis*** - **Vitamin D analogues** such as calcipotriol and calcitriol help treat psoriasis by **inhibiting keratinocyte proliferation** and promoting their differentiation, reducing scale and plaque formation. - They also have **anti-inflammatory properties** that help alleviate the characteristic redness and inflammation seen in psoriatic plaques. - These are commonly used as **topical treatments** for mild to moderate plaque psoriasis. *Pemphigus* - This is an **autoimmune blistering disease** characterized by **antibodies against desmoglein**, leading to loss of cell-cell adhesion in the epidermis. - Treatment primarily involves **systemic corticosteroids** and immunosuppressants, not vitamin D analogues. *Leprosy* - **Leprosy** is a chronic infectious disease caused by **Mycobacterium leprae**, primarily affecting the skin, nerves, upper respiratory tract, eyes, and testes. - Treatment involves **multi-drug therapy (MDT)** with antibiotics like dapsone, rifampicin, and clofazimine, and vitamin D analogues are not indicated. *Lichen planus* - **Lichen planus** is a chronic inflammatory condition affecting the skin, hair, nails, and mucous membranes, characterized by **pruritic, polygonal, purple, planar papules and plaques**. - Treatment typically involves **topical or systemic corticosteroids**, retinoids, or phototherapy, not vitamin D analogues.
Question 8: A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?
- A. Cellulitis
- B. Erythema nodosum (Correct Answer)
- C. Sweet syndrome
- D. Superficial thrombophlebitis
Explanation: ***Erythema nodosum*** - The presentation of **tender, erythematous nodules on the shins**, following a preceding **sore throat**, with associated **joint pain and fatigue**, is highly characteristic of **erythema nodosum**. - It is a form of **panniculitis** typically triggered by infections (e.g., streptococcal pharyngitis), medications, or systemic diseases. *Cellulitis* - Characterized by a **warm, erythematous, swollen area** with poorly defined borders, often accompanied by pain and fever, but typically presents as a diffuse skin infection rather than distinct nodules. - While fever is present, the **nodular nature** of the lesions and their bilateral, symmetrical distribution are less consistent with cellulitis. *Sweet syndrome* - Also known as acute febrile neutrophilic dermatosis, it presents with **tender erythematous plaques or nodules** and **fever**, but typically has a more prominent **neutrophilic infiltrate** histologically. - Lesions of Sweet syndrome often appear on the **upper extremities, face, or neck**, and while it can affect the shins, the clinical picture here is more classic for erythema nodosum, especially given the history of sore throat. *Superficial thrombophlebitis* - Presents as a **palpable, tender, erythematous cord** along the course of a superficial vein, often with localized swelling and warmth. - The lesions are typically **linear or cord-like**, not discrete nodules scattered over the shins, and are directly related to a thrombosed vein.
Question 9: A 16-year-old boy presented with asymptomatic, multiple erythematous annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. What is the most likely diagnosis?
- A. Pityriasis versicolor
- B. Pityriasis alba
- C. Pityriasis rosea (Correct Answer)
- D. Pityriasis rubra pilaris
Explanation: ### Explanation The clinical presentation of multiple erythematous annular lesions with a characteristic **collarette of scales** at the periphery on the trunk is a classic description of **Pityriasis Rosea (PR)**. **Why Pityriasis Rosea is correct:** PR is an acute, self-limiting inflammatory dermatosis, often associated with Human Herpesvirus 6 or 7 (HHV-6/7). It typically begins with a single, large **"Herald Patch"** followed by a generalized eruption of smaller oval lesions. The scales in PR are unique; they are attached at the periphery and free in the center, forming a **"collarette"** appearance. On the back, these lesions follow the lines of cleavage, creating a **"Christmas Tree"** or "Fir Tree" distribution. **Why the other options are incorrect:** * **Pityriasis versicolor:** Presents as hypo- or hyperpigmented macules with fine, branny (furfuraceous) scaling. It is caused by *Malassezia* and does not typically show a peripheral collarette of scales. * **Pityriasis alba:** Commonly seen in children with atopy, presenting as ill-defined hypopigmented patches with fine scaling, usually on the face. It lacks the annular, erythematous nature of PR. * **Pityriasis rubra pilaris (PRP):** Characterized by follicular papules on an erythematous base, "islands of sparing," and orange-red palmoplantar keratoderma. It does not present with a collarette of scales. **High-Yield Clinical Pearls for NEET-PG:** * **Herald Patch:** The initial lesion (seen in 80% of cases), usually larger and more scaly than subsequent lesions. * **Hanging Curtain Sign:** When the skin is stretched across the long axis of the lesion, the scales tend to fold inwards (characteristic of PR). * **Treatment:** Usually conservative (reassurance); antihistamines for pruritus. * **Differential Diagnosis:** Secondary syphilis (always rule this out if lesions involve palms and soles; PR typically spares them).
Question 10: Civatte bodies are a characteristic histological feature of which condition?
- A. Lichen simplex chronicus
- B. Lichen planus (Correct Answer)
- C. Lichen sclerosus
- D. All of the above
Explanation: **Explanation:** **Civatte bodies** (also known as colloid or hyaline bodies) are a hallmark histopathological finding in **Lichen Planus**. They represent apoptotic or degenerated keratinocytes located in the lower epidermis or papillary dermis. **Why Lichen Planus is correct:** Lichen planus is characterized by a "lichenoid" or interface dermatitis where a dense, band-like lymphocytic infiltrate attacks the basal layer of the epidermis. This immune-mediated destruction leads to **liquefactive degeneration** of the basal cells. The shrunken, eosinophilic remnants of these dead keratinocytes are the Civatte bodies. They stain positively for PAS (Periodic Acid-Schiff) and contain IgM on direct immunofluorescence. **Why other options are incorrect:** * **Lichen simplex chronicus:** This is a result of repetitive scratching. Histology shows hyperkeratosis, hypergranulosis, and regular elongation of rete ridges (psoriasiform hyperplasia), but not basal cell apoptosis. * **Lichen sclerosus:** While it involves interface changes, its hallmark is significant subepidermal edema and homogenization of collagen (sclerosis) in the upper dermis, rather than prominent Civatte bodies. **NEET-PG High-Yield Pearls for Lichen Planus:** * **6 P’s:** Planar, Purple, Polygonal, Pruritic, Papules, and Plaques. * **Wickham Striae:** White reticular lines on the surface of lesions (due to focal hypergranulosis). * **Max-Joseph Spaces:** Small clefts between the epidermis and dermis due to extensive basal cell degeneration. * **Saw-tooth Rete Ridges:** Characteristic appearance of the epidermal-dermal junction. * **Koebner Phenomenon:** Development of lesions at sites of trauma (also seen in Psoriasis and Vitiligo).
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