Practice question answers papulosquamous disorders

Practice question answers
Papulosquamous disorders
Updated: 03/05/2019
© Jun Wang, MD, PhD

1. C. Well-demarcated plaque with erythematous base and silver scales is most likely psoriasis, as confirmed by epidermal hyperplasia with elongated rete ridges and absence of granular layers. Dermatophytosis usually has central resolution, peripheral scaling and annular shape, with microscopic findings of neutrophilic infiltration and fungal hyphae identified by special stains. Lichen planus usually presents with pruritic, polygonal purple papules with flat top, and microscopically it has lichenoid inflammation. Seborrheic dermatitis usually presents as erythematous papules and plaques, with yellowish scales, involving seborrheic areas, such as face, especially nasolabial areas. Microscopically it has spongiosis centered on follicles, but usually not elongated rete ridges. Squamous cell carcinoma has cytological atypia.

2. A.  Psoriasis is caused by cornification defects, either due to elevated cytokines, or LCE3 deletion. Autoimmune destruction of keratinocytes can be seen in various dermatosis, including lichen planus, erythema multiforme and allergic contact dermatitis. Chronic inflammation due to fungal infection is seen in dermatophytosis. Malignant transformation caused by UV light is the major cause of skin cancers. Treponema pallidum infection is associated with syphilis.

3. C. Psoriasis is caused by cornification defects, either due to elevated cytokines, or LCE3 deletion. BRAF mutation can be seen in various tumors, including melanocytic nevus and melanoma. FGFR3 abnormality is associated with urothelial papilloma, and certain type of urothelial carcinoma. P53 mutation can be seen in many different cancers, especially high grade cancers. PTCH mutation is seen in basal cell carcinoma.

4. A. Droplike erythematous to salmon-pink papules with fine scales and microscopic findings of epidermal hyperplasia and Munro microabscesses is most likely guttate psoriasis. Lichen planus usually presents with pruritic, polygonal purple papules with flat top, and microscopically it has lichenoid inflammation. Pityriasis rosea has herald patch followed by Christmas tree pattern of erythematous patches with fine pink scale, and microscopic findings of spongiosis, but NOT prominent epidermal hyperplasia. Seborrheic dermatitis usually presents as erythematous papules and plaques, with yellowish scales, involving seborrheic areas, such as face, especially nasolabial areas. Microscopically it has spongiosis centered on follicles, but usually not elongated rete ridges. Secondary syphilis has prominent plasma cell infiltrates.

5. D. Widespread pustules and epidermal hyperplasia with parakeratosis and numerous neutrophilic aggregates, especially at the thinned granular layer, is likely to be pustular psoriasis, especially when the patient has nail changes that are commonly seen associated with psoriasis. Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules, and microscopically it has subepidermal vesicle with neutrophilic aggregates. Pityriasis rosea has herald patch followed by Christmas tree pattern of erythematous patches with fine pink scale, and microscopic findings of spongiosis, but NOT prominent epidermal hyperplasia. Secondary syphilis has prominent plasma cell infiltrates.

6. B. Psoriasis is caused by cornification defects, either due to elevated cytokines, or LCE3 deletion. Autoimmune destruction of keratinocytes can be seen in various dermatosis, including lichen planus, erythema multiforme and allergic contact dermatitis. Chronic inflammation due to fungal infection is seen in dermatophytosis. Hyperglycemia as seen in diabetes is associated with increased risk of infections, but not psoriasis. Patient with malnutrition has symptoms and signs such as weight loss, anemia, etc.

7. B. Small joint tenderness and swelling in a patient with psoriasis, is most likely psoriatic arthritis (sausage fingers). Infectious arthritis usually has leukocytosis. Rheumatic and rheumatoid arthritis have abnormal serology studies.

8. C. Conjunctivitis in a patient with psoriasis, is most likely psoriatic conjunctivitis. The diagnosis of psoriasis is confirmed by biopsy of the skin lesion.

9. D. Seborrheic dermatitis usually presents as erythematous papules and plaques, with yellowish scales, involving seborrheic areas, such as face, especially nasolabial areas. Atopic dermatitis has diffuse facial scaly rash with erythematous base that spares nasal area. Pemphigus erythematosus and SLE have malar rash on face. Psoriasis has well-demarcated papule/plaque with erythematous base and silver scales.

10. D. Seborrheic dermatitis is associated with abnormal immune activity to normal fungal colonization. Autoimmune process is associated with various dermatosis, including pemphigus and bullous pemphigoid. Cornification defects are seen in psoriasis. Viral infection can be associated with various dermatosis, including herpes, pityriasis rosea and erythema multiforme.

11. B. Lichen planus usually presents with pruritic, polygonal purple papules with flat top, and microscopically it has lichenoid inflammation. Dermatophytosis usually has central resolution, peripheral scaling and annular shape, with microscopically identified fungal hyphae. Pityriasis rosea has herald patch followed by Christmas tree pattern of erythematous patches with fine pink scale, and microscopic findings of spongiosis, but NOT lichenoid inflammation. Pustular psoriasis has widespread pustules and epidermal hyperplasia with parakeratosis and numerous neutrophilic aggregates, especially at the thinned granular layer. Secondary syphilis has prominent plasma cell infiltrates.

12. A. Clumped IgM deposit at dermoepidermal junction is seen in lichen planus. IgG deposit at intercellular junctions of keratinocytes, where desmosomes are, is seen in pemphigus. Granular deposit of IgA at dermal papillae is seen in dermatitis herpetiformis. Linear deposit of IgG at dermoepidermal junction is seen in bullous pemphigoid.

13. B. Koebner phenomenon is defined as new skin lesion on areas of cutaneous injury. The etiology is unknown.

14. C. It is not uncommon for lichen planus to be associated with hepatitis C. There is recommendation to test for hepatitis C in patients with lichen planus.

15. B. Lichen planopilaris is lichenoid inflammation involving hair follicles. It is commonly associated with alopecia. Dermatophytosis usually has central resolution, peripheral scaling and annular shape, with microscopically identified fungal hyphae. Psoriasis has well-demarcated papule/plaque with erythematous base and silver scales, and microscopically, epidermal hyperplasia with elongated rete ridges and absence of granular layers. Seborrheic dermatitis usually presents as erythematous papules and plaques, with yellowish scales, involving seborrheic areas, such as face, especially nasolabial areas. Microscopically it has spongiosis centered on follicles, but usually not elongated rete ridges. Secondary syphilis has prominent plasma cell infiltrates.

16. A. Lichen planus is CD8+ T cell-mediated immune reaction against basal epidermal cells or dermoepidermal junction, with unknown triggering factor. Psoriasis is caused by cornification defects, either due to elevated cytokines, or LCE3 deletion. Seborrheic dermatitis is associated with abnormal immune activity to normal fungal colonization. Viral infection can be associated with various dermatosis, including herpes, pityriasis rosea and erythema multiforme.

17. C. See discussion of question 4.

18. B. Pityriasis rosea is usually associated with certain viral infection, including vaccines. Certain human herpes virus, such as HHV6 and HHV7, may cause pityriasis rosea. But there is no known association between pityriasis rosea and human herpes virus 1. Malassezia is associated with seborrheic dermatitis. Treponema pallidum is associated with syphilis. There is no known associated between pityriasis rosea and either EBV or HPV.

19. E. Non-pruritic skin rashes in a patient with history of glans ulcer is highly suspicious for secondary syphilis, which is further supported by diffuse dermal plasma cell infiltrate in this case. Also see discussion of question 4.

20. E. The screening test for syphilis include Rapid plasma regain (RPR) and Venereal Disease Research Laboratory (VDRL), and the confirmation tests include Fluorescent treponemal antibody-absorption (FTA-ABS) or Treponema pallidum hemagglutination assay. Culture is for bacterial infections. Flow cytometry studies is more useful for hematopoietic disorders, especially neoplasia. Monospot is for infectious mononucleosis. RT-PCR for HIV RNA is for HIV infection, which is a high risk for this patient, but irrelevant to his skin rash.

21. A. This is a silver that highlighted fungal hyphae. Dermatophytosis may have various microscopic pattern but fungal hyphae identified by special stains is confirmative for the diagnosis.



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