Evaluation of sweating responses in patients with systemic connective tissue disorders using the quantitative sudomotor axon reflex test

In systemic connective tissue disorders (SCTDs), eccrine sweat glands are frequently attacked by immune cells, as evidenced by pathological observations. Sweating reflects vascular activity through the autonomic nervous system, while few studies have reported sweating ability in SCTDs or the relationship between sweating ability and Raynaud's phenomenon caused by sympathetic hyperreactivity. We performed the quantitative sudomotor axon reflex test on 85 patients diagnosed with systemic sclerosis, mixed connective tissue disease, systemic lupus erythematosus, Sjogren’s syndrome, and dermatomyositis. Evaluations were performed once in summer and once in winter. We investigated the relationship of the axon reflex sweat volume and the reaction time to Raynaud's phenomenon, skin symptoms, and patient background. Most patients did not show a decrease in sweating compared to healthy participants, but patients with systemic sclerosis who were positive for anti-RNA polymerase III antibodies showed little or no sweating. One in three patients showed less sweating in summer than in winter, which is the opposite of the normal seasonal variation. Although no relationship was observed between the sweat volume and the total Raynaud’s condition scores, patients with pain had more sweating than those without pain. These results suggested the possible utility of measuring sweating on autonomic peripheral circulatory disorders.