Repeated USMLE Questions Step 1- Review- 94

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Q- A 7-year-old girl is brought to the clinic by her parents due to severe sunburns after minimal sun exposure. She has also developed freckle-like pigmented lesions on her face and arms. A skin biopsy shows dysplastic keratinocytes and a paucity of melanocytes.

What is the most likely diagnosis?

A- Albinism

B- Atopic dermatitis

C- Neurofibromatosis

D- Tuberous sclerosis

E- Xeroderma pigmentosa

E- Xeroderma pigmentosa- It is a rare genetic disorder that causes extreme sensitivity to ultraviolet (UV) light. Patients often experience severe sunburns after minimal sun exposure. Freckle-like pigmented lesions on sun-exposed areas are a characteristic feature. The defect in DNA repair mechanisms, particularly the excision repair enzymes, leads to dysplastic keratinocytes and a paucity of melanocytes.



Q- A 25-year-old woman presents with a history of recurrent urinary tract infections (UTIs). She reports dysuria, frequency, and urgency associated with each episode. On examination, there is suprapubic tenderness. Urinalysis reveals pyuria. Culture confirms Escherichia coli as the causative organism. The physician considers prescribing prophylactic antibiotics.

Which of the following medications is commonly used for prophylaxis in patients with recurrent UTIs?

A- Amoxicillin

B- Cephalexin

C- Ciprofloxacin

D- Nitrofurantoin

E- Trimethoprim-sulfamethoxazole (TMP-SMX)

D- Nitrofurantoin- It is commonly used for prophylaxis in patients with recurrent urinary tract infections (UTIs). It has the advantage of being effective against many of the common pathogens causing UTIs, including Escherichia coli. Nitrofurantoin is often prescribed in low doses for an extended period as prophylaxis to prevent recurrent UTIs. Other medications on the list may be used to treat acute UTIs but are not typically used for long-term prophylaxis due to concerns about resistance and side effects.

 

Q- A 57-year-old man presents with a sudden onset of severe chest pain that radiates to his back. He describes the pain as tearing in nature. His blood pressure is significantly different between the right and left arms, with a higher reading in the right arm. On auscultation, there is a diastolic murmur heard along the left sternal border. An imaging study confirms the diagnosis.

Which of the following is the most likely cause of this condition?

A- Aortic dissection

B- Aortic regurgitation

C- Aortic stenosis

D- Mitral valve prolapse

E- Tricuspid regurgitation

A- Aortic dissection- This patient’s presentation, including sudden onset of severe tearing chest pain that radiates to the back, significant blood pressure difference between arms, and the diastolic murmur along the left sternal border, is consistent with aortic dissection. Aortic dissection involves a tear in the intimal layer of the aorta, leading to the creation of a false lumen within the vessel wall. Aortic dissection is a medical emergency that requires prompt diagnosis and intervention.



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