Andersen's syndrome: A distinct periodic paralysis

TLDR

Andersen's syndrome is a distinct periodic paralysis characterized by a triad of potassium‑sensitive paralysis, ventricular dysrhythmias, and dysmorphic features, and is genetically distinct from common long‑QT syndromes, though it can be mistaken for them. The study examined 11 additional AS patients from five kindreds. The 11 patients exhibited dysmorphic features, prolonged QT intervals, and paralysis attacks that could be hypokalemic or hyperkalemic, and genetic analysis excluded known sodium channel, potassium channel, and dihydropyridine receptor mutations, confirming Andersen's syndrome as a unique channelopathy affecting both cardiac and skeletal excitability.

Abstract

Abstract A previous study of 4 patients defined Andersen's syndrome (AS) as a triad of potassium‐sensitive periodic paralysis, ventricular dysrhythmias, and dysmorphic features. AS appears to be distinct in terms of its genetic defect from the α‐subunit of skeletal muscle sodium channel and the cardiac potassium channel responsible for most long QT syndromes (LQT1). We studied 11 additional patients with AS from 5 kindreds. Spontaneous attacks of paralysis were associated with hypokalemia, normokalemia, or hyperkalemia. All 11 patients had similar dysmorphic features. The QT interval was prolonged in all patients although only 4 were sympotomatic. Genetic linkage studies excluded linkage to the α‐subunit of the skeletal muscle sodium channel and to four distinct LQT loci. In addition, none of the common dihydropyridine receptor mutations responsible for hypokalemic periodic paralysis were present. We conclude that (1) AS is a genetically unique channelopathy affecting both cardiac and skeletal membrane excitability, (2) attacks of paralysis may be either hypokalemic or hyperkalemic, (3) a prolonged QT interval is an integral feature of this syndrome, and (4) a prolonged QT interval may be the only sign in an individual from an otherwise typical AS kindred. This may be confused with more common, potentially lethal LQT syndromes.