Parálisis periódica hipocalémica familiar: una causa poco frecuente de parálisis flácida aguda

NovelCACNA1Smutation in hypokalaemic periodic paralysis

“…HPP is a rare neuromuscular disorder that presents with sudden and reversible episodes of flaccid paralysis in association with low serum potassium level 3–6. Its estimated prevalence is 1 in 100 000 2 7–9.…”

“…HPP may be primary (familial or sporadic) or secondary to thyrotoxicosis, the latter being exceptional at paediatric age 2 9 10. Primary forms are skeletal muscle ion channelopathies due to point mutations in CACNA1S or SCN4A genes, with a typical onset in the second decade of life 2 4–6. Around 70% of the primary cases are caused by CACNA1S mutations (HPP type 1) and 10%–20% by SCN4A (HPP type 2) 2 5 9 11.…”

“…Around 70% of the primary cases are caused by CACNA1S mutations (HPP type 1) and 10%–20% by SCN4A (HPP type 2) 2 5 9 11. Familial HPP, which accounts for the majority of the cases, has an autosomal dominant mode of inheritance with incomplete penetrance 2 4 9 12 13. Sporadic mutations are responsible for approximately one-third of cases 2 12 13…”

“…Patients suffer intermittent attacks of focal or generalised weakness, predominantly affecting lower limbs, along with hyporeflexia or areflexia, without sensitive impairment or central nervous system affection 2 4 5 9 12 13. Therefore, preservation of reflexes in a paralysed limb, prominent sensory or autonomic symptoms should evoke a different diagnosis 9.…”

“…The frequency of the episodes is highly variable among patients, although it tends to be higher from the second to the fourth decades of life, and then usually decreases 5 9 12 13 15. Episodes are usually triggered by high-carbohydrate and sodium meals, prolonged fasting, alcohol consumption, prolonged rest after intense exercise, cold exposure, acute emotional stress, infections, menstruation, lack of sleep or specific medications (beta-agonists, insulin or corticosteroids) 2–5 9 13. However, spontaneous attacks may occur 12.…”