Source / episode info

• **Episode:**126
• **Title:**Divine Intervention Episode 126 – USMLE Step 2CK Rapid Review Series 7 (IM)
• **Published:**2019-07-23
• Source:Episode page

One-liner

This episode reviews critical high-yield topics including retinoblastoma risk factors, spinal stenosis, gonococcal arthritis management, the workup of CLL and Polycythemia Vera, paraneoplastic syndromes from lung cancer (SCLC/Squamous), neuromuscular junction disorders (MG vs. LEMS), and acid-base physiology related to sleep apnea and diuretics.

High-yield summary

• Retinoblastoma: Associated with the RB1 gene mutation; patients have a significantly increased lifetime risk of developing osteosarcoma, besides other risks like Paget's disease or exposure to PTH analogs (e.g., Teriparatide).
• Paraneoplastic Syndromes: Small Cell Lung Cancer (SCLC) commonly causes SIADH (low serum osmolarity/high urine osmolarity), ACTH excess (Cushingoid features), and antibodies against voltage-gated calcium channels leading to Lambert-Eaton Myasthenic Syndrome (LEMS). Squamous Cell Lung Cancer is classically associated with PTHrP production, causing hypercalcemia.
• Neuromuscular Junction Disorders: The key difference between Myasthenia Gravis (MG) and LEMS is the pattern of muscle weakness: MG worsens with use; LEMS improves with use. Repetitive nerve stimulation testing shows a decremental response in LEMS.
• Hematology: Chronic Lymphocytic Leukemia (CLL) presents in older adults with recurrent infections, marked lymphocytosis, and characteristic "smudge cells" on peripheral smear. Polycythemia Vera is an essential thrombocythemia/polycythemia associated with a JAK2 mutation.
• Acid-Base & Pharmacology: Central Sleep Apnea can be treated with Acetazolamide (a carbonic anhydrase inhibitor), which induces a Type 2 RTA physiology (bicarbonate wasting) and metabolic acidosis, thereby increasing respiratory drive.

Learning objectives

• Differentiate the paraneoplastic syndromes associated with SCLC vs. Squamous Cell Lung Cancer.
• Recognize the classic hematologic findings and management of CLL and Polycythemia Vera.
• Apply knowledge of neuromuscular junction disorders, specifically distinguishing Myasthenia Gravis from Lambert-Eaton Syndrome based on clinical presentation and electrophysiology.
• Analyze acid-base disturbances in chronic respiratory failure (e.g., OSA) and understand the mechanism of action for carbonic anhydrase inhibitors like Acetazolamide.
• Identify risk factors for osteosarcoma following retinoblastoma or Paget's disease.

Board exam buzzwords