Practice question answers, acute inflammatory dermatosis

Practice question answers

Acute inflammatory dermatosis

Updated: 03/05/2019

© Jun Wang, MD, PhD

1. E. Pruritic skin swelling without other abnormalities is most consistent with urticaria. Allergic contact dermatitis is usually pruritic papules and vesicles at the site of contact. Atopic dermatitis is characterized by erythematous, ill-defined scaly and crusted patches and plaques.  Erythema multiforme is characterized by NON-pruritic erythematous papule, macule, blisters and target lesion, usually involving extremities, with or without mucosal involvement or sloughing of skin. Guttate psoriasis is characterized by small droplike erythematous to salmon-pink papules with fine scale. None of these four has marked edematous changes.

2. D. Urticaria is caused by increased vascular permeability, resulted from mast cell activation, or bradykinin activation. Chronic rubbing/scratching usually cause lichenification (thickening of skin), as seen in some atopic dermatitis. Desmosome damage is seen in pemphigus. Hemidesmosome damage is seen in bullous pemphigoid. Lymphocyte mediated keratinocyte injury, a type IV hypersensitivity reaction, is seen in various conditions, including erythema multiforme and allergic contact dermatitis.

3. D. Urticaria is caused by increased vascular permeability, resulted from mast cell activation, or bradykinin activation. Eosinophils will secrete histaminase to balance the effects of mast cells. Fibroblast proliferation is usually associated with chronic process, especially healing. Lymphocyte mediated keratinocyte injury, a type IV hypersensitivity reaction, is seen in various conditions, including erythema multiforme and allergic contact dermatitis. Neutrophils are associated with acute inflammations, especially infections, such as dermatophytosis and herpes, as well as dermatitis herpetiformis.

4. B. This is typical target lesion, associated with erythema multiforme. The patient has involvement of oral mucosa, but no skin sloughing, so it is erythema multiforme major. Dermatophytosis is usually localized lesion with central resolution and annular shape. Guttate psoriasis is characterized by small droplike erythematous to salmon-pink papules with fine scale. Stevens Johnson syndrome has skin sloughing.

5. E. Lymphocyte mediated keratinocyte injury, a type IV hypersensitivity reaction, is seen in various conditions, including erythema multiforme and allergic contact dermatitis. Autoantibodies against BP180 or BP230 are seen in bullous pemphigoid. Cornification defects are seen in psoriasis. Disseminated fungal infection is widespread dermatophytosis. Sweat gland dysfunction is seen in dyshidrotic eczema.

6. E. Erythema multiforme minor and major are more commonly associated with viral infection, while Stevens Johnson syndrome and toxic epidermal necrolysis are more commonly associated with drug reaction. Chemical irritation can cause various skin damages, including irritant contact dermatitis. Fungal infection causes dermatophytosis. UV-light is the major cause of skin cancers, including melanoma, basal cell carcinoma, and squamous cell carcinoma.

7. D. See discussion of question 4. The difference between Stevens Johnson syndrome and toxic epidermal necrolysis is the degree of skin sloughing. SJS is less than 10%, and TEN is more than 30%. Bullous pemphigoid does not have target lesions.

8. C. See discussion of question 6. Brain trauma usually does not cause skin sloughing. Hemidesmosome damage is seen in bullous pemphigoid.

9. A. Scattered vesicular changes in an erythematous background, located in areas likely have direct contact with allergens, with microscopic features including spongiosis and lymphocytic/eosinophilic infiltrate without acantholysis, are most likely allergic contact dermatitis. Bullous pemphigoid is characterized by large tense blisters involving flexor surfaces, trunk and mucosa, and microscopically it has subepidermal blisters. Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules, and microscopically it has subepidermal vesicle with neutrophilic aggregates. Bullous lichen planus usually develops in previous lichen planus, and microscopically it has lichenoid inflammation. Pemphigus vulgaris usually has easily ruptured blisters with painful erosions, and microscopically it has acantholysis.

10. E. See discussion of question 5. Autoantibodies against desmoglein 1 or 3 are seen in pemphigus. IgM deposit at dermoepidermal junction is seen in lichen planus.

11. B. Diffuse facial scaly rash with erythematous base that spares nasal area is most likely atopic dermatitis. Allergic contact dermatitis is usually pruritic papules and vesicles at the site of contact. Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules. Pemphigus erythematosus has lupus like malar rash that usually will involve nose. In addition, both pemphigus and SLE are not common in infants.

12. E. Etiology of atopic dermatitis is not well understood but believed to be associated with environmental factors and defected skin barriers. Autoantibody against phospholipid is more commonly seen in SLE. Cornification defects are seen in psoriasis. Drug reactions usually has associated history, and is not known to be associated with atopic dermatitis. Fungal infection is widespread dermatophytosis.

13. A. Although not quite well understood, atopic dermatitis is an allergic disorder and the patient has a higher risk for other allergic disorders, such as asthma. It posts no risk for skin cancers. It is not really an immunodeficiency disorder, so there is no elevated risk for infection. Malabsorption is more associated with other disorders, such as cystic fibrosis.

14. B. Pruritic lichenfied skin lesion in a patient with history of allergic reactions (asthma) is more likely to be adult type atopic dermatitis. Allergic contact dermatitis is usually pruritic papules and vesicles at the site of contact, with erythematous, papular and vesicular changes. Dermatophytosis usually has central resolution, peripheral scaling and annular shape. Lichen planus. usually presents with pruritic, polygonal purple papules with flat top. Psoriasis is characterized by papules or plaques with scales.

15. D. Elevated levels of IgE is commonly seen in patient with atopic dermatitis, especially in persistent cases.

16. A. Lichenification is a result of chronic irritation, including rubbing and scratching, due to keratinocytic hyperplasia. Fungal infection causes dermatophytosis. Lymphocytic infiltration can be seen in various dermatosis, but usually not associated with lichenfication. Increased vascular permeability, resulted from mast cell activation, or bradykinin activation is seen in urticaria.

17. C. Cytological changes of multinucleation, nuclear molding and chromatin margining are consistent with herpesinfection. When it occurs on top of atopic dermatitis, it is Kaposi varicelliform eruption (eczema herpeticum). Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules, and microscopically it has subepidermal vesicle with neutrophilic aggregates. Irritant contact dermatitis is associated with chemical irritation and has papules or vesicles in a erythematous base. Pustular psoriasis is characterized by widespread pustules on erythematous background. None of these three has the cytological changes of herpes. Shingles are herpes infection with a distribution consistent with specific innervation.

18. C. Small pruritic clear fluid containing vesicles of hands and feet is more likely to be dyshidrotic eczema. Allergic contact dermatitis is usually pruritic papules and vesicles with erythematous base at the site of contact. Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules. Pustular psoriasis is characterized by widespread pustules on erythematous background. Shingles are herpes infection with a distribution consistent with specific innervation.

19. D. Chronic pruritic skin plaque with dry cracked surface and an erythematous base is most likely nummular eczema. Dermatophytosis usually has central resolution, peripheral scaling and annular shape. Lichen planus. usually presents with pruritic, polygonal purple papules with flat top. Psoriasis is characterized by papules or plaques with scales.

20. C. By definition, secondary lesions with identical features of primary lesions that are far away, are ID reactions. The pathophysiology is unclear, but believed to be a local reaction identical to the primary process, in the absence offending factors. This patient has seborrheic dermatitis. Identical lesions occur at a location that is usually not associated with seborrheic dermatitis. This is most consistent with ID reactions. Dermatitis herpetiformis has clusters of small pruritic vesicles or pustules, and microscopically it has subepidermal vesicle with neutrophilic aggregates. Dermatophytosis usually has central resolution, peripheral scaling and annular shape, with microscopically identified fungal hyphae. Kaposi varicelliform eruption (eczema herpeticum) is herpes infection on top of atopic dermatitis. Pustular psoriasis is characterized by widespread pustules on erythematous background, and microscopically it has psoriasiform hyperplasia.

21. E. Very dry skin with irregular cracks and fissures is most likely xerotic eczema. Atopic dermatitis usually has associated history of allergy. Dermatophytosis usually has central resolution, peripheral scaling and annular shape. Lichen planus. usually presents with pruritic, polygonal purple papules with flat top. Psoriasis is characterized by papules or plaques with scales.

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