Altered polyamine levels in skeletal muscle of patients with myasthenia gravis.

Forty patients with myasthenia gravis were tested for polyamine content of the musculus sternothyreoideus removed during thymectomy. Cases with slight muscle alteration were found to show elevated values for all the three polyamines (putrescine, spermidine and spermine) examined with an increased spermidine/spermine ratio. In severe muscular atrophy, however, the high spermidine and spermine levels were accompanied by unchanged putrescine content and spermidine/spermine ratio. Denervational changes in polyamine levels parallel to the degree of muscular damage are useful indicators of the actual grade of muscle atrophy associated with myasthenia gravis. In histologically intact samples, without apparent signs of muscular atrophy the spermidine level and spermidine/spermine ratio were increased in comparison to the control. In addition to being very early signs of denervation, these higher values are possibly the biochemical expression of some adaptive, compensatory hyperfunction of the muscle fibers.