The Etiology of Primary Hyperhidrosis: A Systematic Review

Purpose: Primary hyperhidrosis is a pathological disorder of unknown etiology, affecting 0.6-5% of the population, and causing severe functional and social handicaps. As the etiology is unknown, it is not possible to treat the root cause. Recently some differences between affected and non-affected people have been reported. The aim of this review is to summarize these new etiological data. Methods: Search of the literature was performed in the PubMed/Medline Database and pertinent articles were retrieved and reviewed. Additional publications were obtained from the references of these articles. Results: Some anatomical and pathophysiological characteristics (as well as enzymatic, metabolic, and neurological dysfunctions) have been observed in hyperhidrotic subjects; three main possible etiological factors predominate. A familial trait seems to exist, and genetic loci associated with hyperhidrosis have been identified. Histological differences were observed in sympathetic ganglia of hyperhidrotic subjects: the ganglia were larger and contained a higher number of ganglion cells. A higher expression of acetylcholine and alpha-7 neuronal nicotinic receptor subunit in the sympathetic ganglia of patients with hyperhidrosis has been reported. Conclusions: Despite these accumulated data, the etiology of primary hyperhidrosis remains obscure. Nevertheless, three main lines for future research seem to be delineated: genetics, histological observations, and enzymatic studies.