HY Q#5 USMLE Derm Concept Step 2CK

​Step 2ck/ 3 level (inspired from UWORLD) ​

30M w/ rash over her elbows. Rash was first seen 6 weeks ago and it has progressively worsened. She experiences itchiness. Remainder of the skin exam is normal. What is the initial treatment ?  ​

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A. Oral Corticosteroids

B. Topical High potency corticosteroids

C. Topical Low potency corticosteroids 

D. Systemic Methotrexate 

E. Ultravoilent B phototherapy 

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​Explanation: ​

Summary = Correct answer is High potentcy topical steriods which can easily penetrate the extensor surfaces of the psorasis. 

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The reason we get itching in psoriatic skin shows increased nerve fiber density and overexpression of neuropeptides like: Substance P Calcitonin gene-related peptide (CGRP). These stimulate itch fibers (C-fibers), enhancing the sensation of itching.

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✅ B. Topical High potency corticosteroids --> High potency topical corticosteroids in the first 4 weeks to penetrate the thick plaques 

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❌A. Oral Corticosteroids --> Systemic (eg, oral) corticosteroids are typically not used due to the availability of safer systemic treatments.  Also, systemic corticosteroids carry an increased risk for pustular psoriasis or erythrodermic psoriatic flares on discontinuation. 

❌ C. Topical Low potency corticosteroids --> recommended for thin-skinned areas due to the risk for corticosteroid-induced skin atrophy; they are not as effective on extensor areas with thick psoriatic plaques

❌ D. Systemic Methotrexate --> for more than 5 to 10 percent of BSA where topical treatments are extensive and impractical 

❌ E. Ultravoilent B phototherapy --> for more than 5 to 10 percent of BSA where topical treatments are extensive and impractical 

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1. Selective Targeting: UVB radiation specifically targets the skin cells in the upper layers of the skin (epidermis) where psoriasis manifests, making it effective without causing significant damage to deeper layers.

2. Slowing Cell Proliferation: Psoriasis is characterized by an accelerated proliferation of skin cells. UVB exposure slows down the excessive growth and turnover of these cells, helping to normalize the skin's cycle.

3. Reducing Inflammation: UVB has anti-inflammatory effects. It can decrease the infiltration of immune cells that contribute to the inflammatory process in psoriasis, leading to reduced redness and irritation.

4. Promoting Apoptosis: UVB radiation can induce apoptosis (programmed cell death) in the excess skin cells, helping to clear psoriatic plaques.

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