Nelson Textbook of Pediatrics 22nd Edition — Episodic weakness with potassium alterations. Hypokalemic PP (CACNA1S, SCN4A), hyperkalemic PP (SCN4A), Andersen-Tawil (KCNJ2: periodic paralysis + prolonged QT + dysmorphism), paramyotonia congenita, myotonia congenita (CLCN1). Triggers, acute treatment, chronic prevention (acetazolamide, mexiletine).
🌐 paeds.online — Pakistan's Pediatric Platform| Condition | Gene (Channel) | Triggers | Acute Treatment | Chronic Treatment |
|---|---|---|---|---|
| Hypokalemic periodic paralysis | CACNA1S (Ca) / SCN4A (Na) | High-carb meal, rest after exercise, insulin | Oral potassium (0.25-0.5 mEq/kg), avoid IV (rebound hyperkalemia) | Acetazolamide, dichlorphenamide, potassium-sparing diuretics |
| Hyperkalemic periodic paralysis | SCN4A (Na) | Potassium load, rest after exercise, cold | Glucose, calcium, beta-agonist (albuterol) | Acetazolamide, thiazides, low-potassium diet |
| Andersen-Tawil syndrome | KCNJ2 (K) | Rest after exercise, carbohydrates | Potassium if hypokalemic | Acetazolamide, potassium supplements, ICD for arrhythmias |
| Paramyotonia congenita | SCN4A (Na) | Cold exposure, exercise | Warmth, mexiletine | Mexiletine, avoid cold |
| Myotonia congenita (Thomsen AD) | CLCN1 (Cl) | Rest after rest (warm-up phenomenon improves) | Mexiletine, phenytoin, carbamazepine | Mexiletine, exercise warm-up |
| Myotonia congenita (Becker AR) | CLCN1 (Cl) | Rest after rest, transient weakness after rest | Mexiletine | Mexiletine |
Most common in East Asian males. Associated with hyperthyroidism (Graves disease). Acute attack: hypokalemia, treat with oral potassium + propranolol. Definitive: treat hyperthyroidism (methimazole).
Andersen-Tawil triad: 1) Periodic paralysis, 2) Ventricular arrhythmias (prolonged QT, VT, risk sudden death), 3) Dysmorphic features (short stature, low-set ears, micrognathia, clinodactyly). ICD often indicated.