- myotonia permanens
- a rare autosomal dominant myotonia characterized by severe myotonia and hypertrophy of muscles around the neck and shoulders, aggravated by potassium intake, but not associated with muscle weakness. Like myotonia fluctuans and several other disorders, it is due to mutation in the SCNA4A gene (locus: 17q23.1-q25.3), which encodes a subunit of a voltage-gated sodium channel.
Medical dictionary. 2011.