This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today’s case focuses on a 19-year-old who comes to the office because of worsening acne. She has had multiple bouts of acne affecting her shoulders, chest, and face. Her acneiform lesions have increased in size, transforming into nodules, thereby affecting her appearance. She is sexually active with her boyfriend and uses condoms consistently. She does not use tobacco, alcohol, or illicit drugs. Which of the following laboratory investigations should be performed before initiating this drug? Can you figure it out?
A 19-year-old woman comes to the office because of worsening acne. She has had multiple bouts of acne affecting her shoulders, chest, and face. The acne was treated with topical benzoyl peroxide and oral antibiotics with a slight improvement over the past three months. She is concerned because recently, her acneiform lesions have increased in size, transforming into nodules, thereby affecting her appearance. The patient immigrated from India with her family ten years ago. Past medical history is noncontributory. She is sexually active with her boyfriend and uses condoms consistently. She does not use tobacco, alcohol, or illicit drugs. After performing a complete physical examination, a decision to start oral isotretinoin is made. Which of the following laboratory investigations should be performed before initiating this drug?
A. Pulmonary function test
B. Urine ꞵ-hCG testC. Eye examination
D. International normalized ratioE. Purified protein derivative test
Scroll down to find the answer!
The correct answer to today’s USMLE® Step 1 Question is…
B. Urine ꞵ-hCG test
Before we get to the Main Explanation, let’s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
The incorrect answers to today’s USMLE® Step 1 Question are…
A. Pulmonary function test
Incorrect: Baseline pulmonary function testing is recommended before the initiation of amiodarone as it has a high tendency to cause pulmonary toxicity. Isotretinoin is not reported to affect the lung parenchyma.
C. Eye examination
Incorrect: Hydroxychloroquine, a medication used to treat systemic lupus erythematosus, is typically a well-tolerated and safe drug; however, there is a small risk of retinal toxicity in patients with prolonged use. Therefore, patients should have a baseline ophthalmologic evaluation with periodic assessment.
D. International normalized ratio
Incorrect: A baseline international normalized ratio (INR) should be obtained prior to warfarin administration to monitor its activity and prevent unwanted bleeding diathesis. Isotretinoin does not affect INR level.
E. Purified protein derivative test
Incorrect: A purified protein derivative (PPD) test is recommended before administering immunosuppressive drugs like infliximab, an anti-TNF agent, to prevent the reactivation of underlying latent tuberculosis. Isotretinoin does not compromise the immune system.
Main Explanation
Acne vulgaris, an inflammatory skin condition with multifactorial etiology (follicular hyperkeratinization, increased sebum production, and infection by Cutibacterium acnes), can present with inflammatory papules, pustules, or nodules. Treatment options depend on the severity and include retinoids, benzoyl peroxide, antibiotics, and isotretinoin.
This patient suffering from nodulocystic acne needs treatment with oral isotretinoin. Isotretinoin is a known teratogen, and pregnancy should be actively ruled out by measuring serum or urine beta-hCG levels twice. Sexually active patients should be started on two different types of contraception before its initiation. Other standard pretreatment tests include a liver function test and lipid panel (serum triglyceride and cholesterol levels).
Isotretinoin, a retinoid, is a last resort for treating severe (nodulocystic acne with scarring) or unresponsive acne vulgaris. It acts by shrinking the sebaceous glands (reducing sebum production), inhibiting the growth of Cutibacterium acnes, and preventing the formation of comedones. It has several adverse effects, including teratogenicity (craniofacial, cardiac, thymic, and central nervous system malformations), cheilitis, xerosis, conjunctivitis, pruritus, photosensitivity, and hypertriglyceridemia. It can also cause decreased bone mineral density, hepatotoxicity, fatigue, and lethargy.
Major Takeaway
Isotretinoin, a retinoid, treats severe or unresponsive acne. It acts by decreasing sebum production, inhibiting the growth of Cutibacterium acnes, and preventing comedogenesis. Significant adverse effects include teratogenicity, cheilitis, xerosis, conjunctivitis, pruritus, photosensitivity, and hypertriglyceridemia.
References
Vallerand, I. A., Lewinson, R. T., Farris, M. S., Sibley, C. D., Ramien, M. L., Bulloch, A. G. M., & Patten, S. B. (2018). Efficacy and adverse events of oral isotretinoin for acne: a systematic review. British Journal of Dermatology, 178(1), 76-85.
Layton, A. (2009). The use of isotretinoin in acne. Dermato-endocrinology, 1(3), 162-169. _________________________
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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.
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