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Burmese Hypokalemia (BHK)
| Acronym: | BHK |
| Gene: | WNK4 |
| Mutation: | c.2899C>T |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Burmese hypokalemia is a condition connected to a low potassium ions concentration level in the blood serum. Potassium is the most abundant cation in mammals and plays a crucial role in the function of nervous tissue and muscle (skeletal, cardiac, and smooth) throughout the body. To maintain ideal body homeostasis, potassium excretion and dietary intake must be balanced. Abnormalities of potassium homeostasis can occur as a primary condition, or as a secondary disorder.
Burmese hypokalemia or Burmese hypokalemic periodic polymyopathy (BHP) is a disease characterized by muscle weakness associated with intermittent hypokalemia. Signs of Burmese hypokalemia are classically episodic, but in some cats weakness is incessant. During an episode, cats can present with severe generalized muscle weakness, although more commonly weakness of the cervical muscles as evidenced by ventroflexion of the head and neck, head bobbing, and dorsal protrusion of the scapulae. The gait becomes short and maximal recruitment of motor units gives rise to muscle tremors. Cats with more generalized weakness have a crouching gait, especially evident in the hind limbs.
The disease usually becomes evident when kittens are two to six months of age, although some cases have not been detected until 2 years of age. Clinical signs may be triggered by stress or exercise. In some patients, the condition improves spontaneously or with therapy over a period of time, with some cats eventually not requiring ongoing medication. However, some cats with Burmese hypokalemia have lifetime requirements for potassium supplementation. BHP is caused by a missense mutation in the WNK4 gene. The condition is inherited in a recessive autosomal way. The frequency of the affected allele in the breeding population is 14,9%. Genetic tests for Burmese hypokalemia can assist breeders to avoid mating that could generate affected cats and identifying carrier cats that could be excluded from the breeding program.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Fyfe, J.C., Kurzhals, R.L., Hawkins, M.G., Wang, P., Yuhki, N., Giger, U., Van Winkle, T.J., Haskins, M.E., Patterson, D.F., and Henthorn, P.S. (2007). A complex rearrangement in GBE1 causes both perinatal hypoglycemic collapse and late-juvenile-onset neuromuscular degeneration in glycogen storage disease type IV of Norwegian forest cats. Mol. Genet. Metab. 90, 383–392.
Shelton, L., and Helmrich, H.G. (2006). Heritable diseases and abnormalities in cats.