Source / episode info
- **Episode:**324
- **Title:**Divine Intervention Episode 324 – USMLE Step 2CK Rapid Review Series 60 (+ 2CK/3 Course Reminder).
- **Published:**2021-07-06
- Source:Episode page
One-liner
This episode provides rapid review on critical board topics including medulloblastoma with CSF spread, managing TMP-SMX toxicity in HIV patients, diagnosing fatty acid oxidation defects (hypoketotic hypoglycemia), differentiating autoimmune/vascular pathologies (PANDAS/FMD), and mastering the diagnosis and treatment of hereditary spherocytosis.
High-yield summary
- Medulloblastoma: A common pediatric brain tumor that characteristically spreads via the Cerebrospinal Fluid (CSF) pathways, often originating in the cerebellar vermis.
- TMP-SMX Toxicity: Trimethoprim/sulfamethoxazole can cause hyperkalemia by blocking the {Na}^+/{K}^+ exchange mechanism in the collecting duct principal cells and can cause bone marrow suppression due to folate synthesis inhibition, requiring rescue with Leucovorin (folenic acid analog).
- Hereditary Spherocytosis (HS): A membrane defect (e.g., spectrin, band 3) leading to spherocytes, elevated MCHC, and extravascular hemolysis; the treatment of choice is splenectomy.
- FMD vs Stenosis: Resistant hypertension requires differentiating between Fibromuscular Dysplasia (media layer involvement/smooth muscle defect) and atherosclerotic renal artery stenosis (intima layer involvement).
- Fatty Acid Oxidation Defects: Present as a triad of hypoglycemia, hypoketotic state, and often metabolic acidosis (due to secondary lactic acid build-up), because the inability to generate acetyl-CoA prevents ketone body formation.
Learning objectives
- Differentiate the pathophysiology and clinical presentation of medulloblastoma versus other CNS malignancies.
- Recognize drug toxicities associated with TMP-SMX, including hyperkalemia and bone marrow suppression.
- Apply knowledge of red blood cell membrane defects to diagnose hereditary spherocytosis and determine appropriate management (splenectomy).
- Distinguish between the vascular layers affected by Fibromuscular Dysplasia and atherosclerotic stenosis in the renal arteries.
- Correlate metabolic findings (hypoglycemia, hypoketotic state) with fatty acid oxidation disorders.
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