Severe infantile hyperkalaemic periodic paralysis and paramyotonia congenita: broadening the clinical spectrum associated with the T704M mutation in SCN4A.

Describes an Italian kindred with nine individuals affected by hyperkalemic periodic paralysis associated with paramyotonia congenita. Severe periodic paralysis with several episodes a day lasting for hours; Observation that the paralytic episodes were refractory to treatment; Minimal paramyotonia, mainly of the eyelids and hands; Finding that all affected family members carried the threonine to methionine substitution at codon 704 in exon 13 of the skeletal muscle voltage gated sodium channel gene.