Source / episode info
- **Episode:**355
- **Title:**Divine Intervention Episode 355 – USMLE Step 2CK/3 Rapid Review Series 67
- **Published:**2021-12-03
- Source:Episode page
One-liner
This episode reviews the management of Herpes Zoster with acyclovir and nephrolithiasis risk; details the workup of resistant hypertension using PAC/PRA ratio to differentiate primary hyperaldosteronism from renal artery stenosis or fibromuscular dysplasia; and covers the diverse causes and clinical implications of gynecomastia.
High-yield summary
- Herpes Zoster: Vesicular lesions on an erythematous base with sharp, pink borders suggest Herpes Zoster (shingles). Treatment requires antiviral agents like acyclovir, which function as false nucleotides inhibiting DNA synthesis.
- Nephrolithiasis Risk: Drugs that increase nephrolithiasis risk include: 1) Acyclovir (due to crystal formation); 2) Loop diuretics (by increasing urinary calcium excretion, leading to precipitation); and 3) Trimethoprim-sulfamethoxazole (TMP-SMX).
- Primary Hyperaldosteronism (Conn Syndrome): Suspected when a patient presents with resistant hypertension, hypokalemia, and metabolic alkalosis. Diagnosis is strongly suggested by a high plasma aldosterone to renin ratio (PAC/PRA > 30).
- RAS vs FMD: Pathophysiology dictates the difference: Renal Artery Stenosis (RAS) involves atherosclerosis of the intima; Fibromuscular Dysplasia (FMD) affects the vascular media.
- Aldosterone Antagonists: Drugs like Spironolactone and Eplerenone are used for Conn Syndrome. Spironolactone is particularly notable because it also blocks androgen receptors, leading to a risk of gynecomastia.
Learning objectives
- Differentiate the pathophysiology of renal artery stenosis (atherosclerosis) versus fibromuscular dysplasia (media defect).
- Recognize the classic clinical triad and diagnostic lab findings for primary hyperaldosteronism.
- Understand the mechanisms by which various drugs (e.g., acyclovir, loop diuretics) can precipitate nephrolithiasis.
- Apply knowledge of aldosterone receptor antagonists, including their side effects and appropriate use in heart failure.
- Correlate endocrine symptoms (hypokalemia, metabolic alkalosis) with mineralocorticoid excess.
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