Introduction

• Hyperkalemic periodic paralysis   Muscle: hyperkalemic periodic paralysis  (HPP) was first reported in 1985/1986.
• It is the result of an autosomal dominant mutation in the gene for skeletal muscle sodium channels.
• Most affected horses are heterozygotes. Homozygotes show more severe clinical signs, about half die before a year of age but others become adults and may appear to be clinically normal.
• Affected horses seem to be descendants of a show Quarterhorse stallion named Impressive(which is why the complication is sometimes called 'Impressive syndrome').

Clinical signs

Predisposing factors

Etiology

Treatment

Test for HPP

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Naylor J M, Nickel D D, Trimino G et al (1999) Hyperkalaemic periodic paralysis in homozygous and heterozygous horses: a co-dominant genetic condition. Equine Vet J 31 (2), 153-159 PubMed.
• Naylor J M (1997) Hyperkalemic periodic paralysis. Vet Clin North Am Equine Pract 13 (1), 129-144 PubMed.
• Carr E A, Spier S J, Kortz G D & Hoffman E P (1996) Laryngeal and pharyngeal dysfunction in horses homozygous for hyperkalemic periodic paralysis. JAVMA 209 (4), 798-803 PubMed.
• Naylor J M (1994) Equine hyperkalemic periodic paralysis: review and implications. Can Vet J 35 (5), 279-285 PubMed.
• Robertson S A, Green S L, Carter S W et al (1992) Postanesthetic recumbency associated with hyperkalemic periodic paralysis in a quarter horse. JAVMA 201 (8), 1209-1212 PubMed.
• Traub-Dargatz J L, Ingram J T, Stashak T S et al (1992) Respiratory stridor associated with polymyopathy suspected to be hyperkalemic periodic paralysis in four quarter horse foals. JAVMA 201 (1), 85-89 PubMed.

Organization(s)

• American Quarterhorse Association, PO Box 200, Amarillo, Texas 79168, USA. Tel: +1 (806) 376 4811; Website: http://www.aqha.com.
• Gene probe testing:
  • Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616-8744, USA.