Endocrinology (periodic hypokalemic polymyopathy in Burmese and closely related cats)

Question 1

What is the cause of periodic hypokalemic polymyopathy

Answer 1

Altered function of WNK4 gene in Burmese cats causes sufficient potassium loss into the urine to result in symptomatic hypokalemia

This in turn causes muscle weakness and polymyopathy

Question 2

What is the signalment of cats suffering from periodic hypokalemix polymyopathy

Answer 2

Most affected cats first develop clinical signs when 2-10 months of age
- The majority of them by 4-6 months

All cases observed in Burmese, Bombay and Tonkinese cats

Question 3

What are the typical clinical findings

Answer 3

The key findings reflect muscle weakness due to hyperpolarisation of the muscle cell membrane and possibly muscle pain
- Weakness of the neck (i.e. passive ventroflexion of the head and neck)
- Weakness of the thoracic limb girdle
- Head bobbing during locomotion
- Appendicular weakness that can affect only the forelimbes, only the hindlimbs or a combination of the four limbs (inability to jump, hindlimb paresis, tremors more prominent in the thoracic limbs)

Question 4

What is the clinical course of the periodic hypokalemic polymyopathy

Answer 4

The problem is generally episodic or periodic but there is no consistent pattern

Stress is an important trigger

Question 5

How can you investigate the disease

Answer 5

Demonstration of a serum potassium concentration < 3.0 mmol/ at the same time as the patients displays characteristic signs

High to very high serum CK

Molecular genetic testing

Question 6

What is the treatment for periodic hypokalemic polymyopathy

Answer 6

Oral potassium replacement therapy is generally the best way to increase the serum potassium concentration

In cats where it is difficult to re-establish normal serum potassium using oral supplementation alone, adding spironolactone (1-2 mg/kg q12-24h) can be helpful