Hypermyelination and overexpression of neuregulin-1 in thoracic sympathetic nerves in patients with primary palmar hyperhidrosis.

Primary palmar hyperhidrosis (PPH) is a condition characterized by high levels of palmar perspiration in excess of physiological need. The etiopathogenesis of PPH is thought to be related to hyperactivity of the sympathetic system, but the exact mechanism is still obscure. The aim of this study was to observe the ultrastructure of the thoracic sympathetic nerves and measure the expression of neuregulin-1 (Nrg-1) in thoracic sympathetic nerve tissue in patients with PPH relative to control subjects. Samples of T3 sympathetic ganglia were obtained from 58 subjects: 30 PPH patients who underwent endoscopic thoracic sympathectomy and 28 control subjects who underwent pleurectomy for chronic empyema. The ultrastructure of the myelin sheath of the sympathetic axons was observed using electron microscopy, and the thickness of the myelin sheath was compared between the two groups. Expression of Nrg-1 mRNA in thoracic sympathetic nerve tissue was evaluated using reverse transcription-polymerase chain reaction analysis. Subjects in the hyperhidrosis group had a significantly greater average myelin thickness and a significantly lower g-ratio relative to the control group. The hyperhidrosis group had significantly higher relative expression of Nrg-1 mRNA in thoracic sympathetic nerve tissue. Hypermyelination of the thoracic sympathetic axons is probably one pathogenetic mechanism underlying PPH. Nrg-1 is likely to be an important cause of hypermyelination in thoracic sympathetic axons in patients with PPH.