Source / episode info

• **Episode:**502
• **Title:**Divine Intervention Episode 502: USMLE Step 2/3 Rapid Review Series 109
• **Published:**2024-01-12
• Source:Episode page

One-liner

This episode provides a rapid review covering infectious disease diagnostics (Toxoplasmosis, Vaginitis), genetic syndromes (TSC, Turner), pulmonary pathology (Asbestosis), and lymph node architecture changes associated with viral infections (EBV/Mono).

High-yield summary

• Toxoplasmosis in HIV: In patients with CD4 count < 100 cells/L, ring-enhancing brain lesions suggest Toxoplasma gondii. Prophylaxis is TMP-SMX. Treatment is Pyrimethamine + Sulfadiazine.
• Vaginal Discharge Diagnosis: pH and microscopy are key. Candida (yeast) shows pseudo-hyphae, {pH} 4.5. Bacterial Vaginosis (BV) shows clue cells, {pH} > 4.5. Trichomoniasis shows motile protozoa.
• Tuberous Sclerosis Complex (TSC): A phakomatosis characterized by three classic findings: renal angiomyolipomas, ash leaf spots (hypopigmented macules), and cardiac rhabdomyomas. It is associated with a deletion at chromosome 20q.
• Asbestosis: Causes restrictive lung disease and elevated {A-a} gradient due to thickened diffusion distance. Pleural plaques are characteristic, but the most common malignancy risk is Bronchogenic Carcinoma, not mesothelioma.
• Lymph Node Architecture (Mono): Viral infections cause hyperplasia in the T cell zone (Paracortex). Immunodeficiency or B cell maturation defects lead to absent/hypoplastic germinal centers.
• Turner Syndrome: Characterized by 45, XO karyotype and often presents with streak ovaries (gonadal dysgenesis), hypergonadotropic hypogonadism, and increased risk of coarctation of the aorta.

Learning objectives

• Differentiate between common causes of vaginitis based on \text{pH} and microscopy.
• Identify the classic clinical triad and genetic basis of Tuberous Sclerosis Complex (TSC).
• Interpret pulmonary findings associated with asbestos exposure, including characteristic imaging and gas exchange abnormalities.
• Recognize the key laboratory and physical exam findings in Turner syndrome and other sex chromosome aneuploidies.
• Correlate lymph node architectural changes (paracortex vs. germinal center) with specific immunodeficiency states or viral infections.