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Hyperkalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness, usually beginning in infancy or early childhood. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Episodes tend to increase in frequency until about age 25, after which they may occur less frequently. Factors that can trigger attacks include rest after exercise, potassium-rich foods, stress, fatigue, and periods without food (fasting). Muscle strength improves between attacks, although many affected people continue to experience mild stiffness (myotonia), particularly in muscles of the face and hands.
Some people with hyperkalemic periodic paralysis have increased levels of potassium in their blood (hyperkalemia) during attacks. In other cases, attacks are associated with normal blood potassium levels (normokalemia). Ingesting potassium can trigger attacks in affected individuals, even if blood potassium levels do not go up.
Hyperkalemic periodic paralysis affects an estimated 1 in 200,000 people.
Mutations in the SCN4A gene cause hyperkalemic periodic paralysis.
The SCN4A gene provides instructions for making a protein that plays an essential role in muscles used for movement (skeletal muscles). For the body to move normally, these muscles must tense (contract) and relax in a coordinated way. Muscle contractions are triggered by the flow of certain positively charged atoms (ions), including sodium, into muscle cells. The SCN4A protein forms channels that control the flow of sodium ions into these cells.
Mutations in the SCN4A gene alter the usual structure and function of sodium channels. The altered channels cannot properly regulate the flow of sodium ions into muscle cells, which reduces the ability of skeletal muscles to contract. Because muscle contraction is needed for movement, a disruption in normal ion transport leads to episodes of muscle weakness or paralysis.
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
In most cases, an affected person has one parent with the condition.
'''Hyperkalemic periodic paralysis''' ('''HYPP'''), also known as '''Impressive Syndrome''', is an genetic disease autosomal dominant disorder which affects ion channelss in muscle cells and the ability to regulate potassium levels in the blood of horses. This inherited disease is characterized by uncontrollable muscle twitching and substantial muscle weakness or paralysis among affected horses. HYPP is a dominant disorder; therefore heterozygotes bred to genotype normal horses will still likely produce clinically affected offspring 50% of the time. The disease is contained to the bloodline of the famous Appendix American Quarter Horse stallion Impressive (horse), who has over 55,000 living descendants as of 2003. Although the disease is primarily limited to the American Quarter Horse breed and closely related breeds such as American Paint Horses and Appaloosas at this time, cross-breeding has begun to extend it to grade horses and ponies. The spread of the disease is perpetuated by the favorable judgings given to diseased horses in showing, due in part to involuntary muscle twitching which helps to build large, bulky muscles that judges favor. In 1994, researchers at the University of Pittsburgh, with a grant from various horse organizations, isolated the gene responsible for the problem and developed a blood test for it. Using this test, horses may be identified as: * H/H, meaning they have the gene and it is homozygous. These horses always pass on the disease. * N/H, meaning they have the gene and it is heterozygous. These horses are affected to a lesser degree, and pass on the disease 50% of the time. * N/N, meaning they do not have the disease and cannot pass it on, even if they are a descendant of Impressive. Recently, horse organizations have begun instituting rules to attempt to eliminate this widespread disease. The American ... [ Read More ]
Ment 2 Be Farms - Standing bay tovero, cremello quarter horse, and red roan miniature at stud. Includes sales list, photos, and profiles of horses. Offers boarding and horses for lease. Contains articles on Hyperkalemic Periodic Paralysis Disease (HYPP) and Lethal White Overo Syndrome. Also breeds Jersey dairy cattle. Located in Towanda.
KMK Paint Horses - Standing chestnut overo and sorrel overos at stud. Includes sales list, photos, and profiles of horses. Contains foaling camera, a message board, a chat room, and information on Hyperkalemic Periodic Paralysis (HYPP) and Lethal White Overo Syndrome. Located in York.
Cross 5 Ranch - Standing sorrel breeding stock at stud. Includes sales list, photos, and profiles of horses. Contains information on Hyperkalemic Periodic Paralysis (HYPP) and Lethal White Overo Syndrome. Located in Buckeye.
Cross 5 Ranch - Standing sorrel breeding stock at stud. Includes sales list, photos, and profiles of horses. Contains information on Hyperkalemic Periodic Paralysis (HYPP) and Lethal White Overo Syndrome.