EC Paediatrics

Introduction: Periodic Paralysis (PP) is a rare neuromuscular disease related to a defect in muscle ion channels, characterized by sporadic episodes of painless muscle weakness that can be precipitated by vigorous exercise, prolonged fasting, or carbohydrate-rich meals. PP is classified as hypokalemic when episodes occur associated with low levels of potassium in the blood. The crises start in late childhood or early adolescence and vary in frequency and duration. Treatment during the acute phase is administration of potassium chloride [1-4].

Case Report: A 12-year-old female adolescent appealed to the emergency department due to sudden onset of tetraparesis. She had no difficulty breathing or signs of respiratory distress. Neurological examination showed grade II muscle strength in the lower limbs and grade III in the upper limbs. Osteotendinous reflexes were absent. Facial mimic was present.

The mother promptly reported a family history of periodic hypokalemic paralysis affecting several members.

Blood analysis showed an isolated severe hypokalemia of 1.7 - 2.0 mEq/L. Electrocardiogram (EKG) showed prolonged PQ interval, mild ST depression, prominent U waves.

Slow correction of potassium was promptly started with gradual recovery of muscle strength and EKG stabilization. She was discharged 20 hours after therapy onset and medicated at home with daily acetazolamide and potassium chloride if onset of symptoms. Genetic study was started for index familial mutations.

Conclusion: Periodic familial paralysis are rare conditions, the most frequent being the hypokalemic form. The diagnosis of PP can be confirmed by genetic tests, which are recommended as first line when there is an intermediate to high degree of clinical suspicion. This case report is intended to emphasize the importance of the clinical history and a complete physical examination on diagnosis. Treatment should not be delayed. Genetic family counselling should be offered [2,3].

Keywords: Periodic Paralysis (PP); Potassium Chloride; Electrocardiogram (EKG)

1. Fontaine B., et al. “Periodic paralysis and voltage-gated ion channels”. Kidney International1 (1996): 9-18.
2. Statland JM., et al. “Review of diagnosis and treatment of periodic paralysis”. Muscle and Nerve (2018): 522-530.
3. Fontaine B., et al. “Mapping of the hyopokalaemic periodic (HypoPP) locus to chromosome 1q31-32 in the three European families”. Nature Genetics (1994).
4. Venance SL., et al. “The primary periodic paralyses: diagnosis, pathogenesis and treatment”. Brain 129 (2006): 8-17.
5. Kung AW. “Clinical review: Thyrotoxic periodic paralysis: a diagnostic challenge”. The Journal of Clinical Endocrinology and Metabolism 91 (2006): 2490.
6. Ptácek LJ., et al. “Dihydropyridine receptor mutations cause hypokalemic periodic paralysis”. Cell 77 (1994): 863.
7. Matthews E., et al. “Voltage sensor charge loss accounts for most cases of hypokalemic periodic paralysis”. Neurology 72 (2009): 1544.
8. Sternberg D., et al. “Hypokalaemic periodic paralysis type 2 caused by mutations at codon 672 in the muscle sodium channel gene SCN4A”. Brain 124 (2001): 1091.
9. Bulman DE., et al. “A novel sodium channel mutation in a family with hypokalemic periodic paralysis”. Neurology 53 (1999): 1932.
10. Miller TM., et al. “Correlating phenotype and genotype in the periodic paralyses”. Neurology 63 (2004): 1647.
11. Ober KP. “Thyrotoxic periodic paralysis in the United States. Report of 7 cases and review of the literature”. Medicine 71 (1992): 109.