Reversible nutritional myopathy with myotonia in the protein-deficient rat given methionine.

Rats fed a protein-deficient synthetic diet developed hind limb weakness caused by a myopathy with myotonic features on electromyography. Deficiency of vitamin E and selenium, known causes of nutritional myopathy, were excluded. Methionine supplementation of the diet reversed the clinical signs of weakness within 12 h.