Rare high-risk conditions carry disproportionately high morbidity/mortality if not recognized promptly. Pheochromocytoma: catecholamine-secreting tumor (usually adrenal) causing episodic hypertensive crises with the 5 Ps (Pressure, Pain/headache, Perspiration, Palpitations, Pallor). Alpha-blockade BEFORE beta-blockade is critical. Malignant hyperthermia: pharmacogenetic disorder triggered by succinylcholine or volatile anesthetics in RYR1 mutation carriers, causing uncontrolled calcium release, rigidity, hyperthermia, rhabdomyolysis. Treatment: dantrolene IV. Addisonian crisis: acute adrenal insufficiency with hypotension refractory to fluids, hyponatremia, hyperkalemia, hypoglycemia. Treatment: IV hydrocortisone 100 mg STAT. Thyroid storm: decompensated thyrotoxicosis with fever, tachycardia, altered mental status. Treatment sequence: PTU first → iodine 1 hour later (PTU must block synthesis before iodine blocks release).