Possible role of Helicobacter pylori in diseases of dermatological interest.

Helicobacter pylori is a gram-negative, flagellate, microaerophilic bacterium identified for the first time about 30 years ago, as a pathogenic factor of gastritis and peptic ulcer. Soon after, it was linked to several gastrointestinal and extra-gastrointestinal diseases (hematological, cardiovascular, neurological, pulmonary and ocular diseases, obesity, diabetes mellitus, growth retardation and extragastric MALT lymphoma). Association and possible cause-effect correlation with H. pylori infection were suggested in diseases of dermatological interest such as chronic urticaria, rosacea, Henoch-Schoenleins purpura, idiopathic thrombocytopenic purpura, cutaneous and oral lichen planus, atopic dermatitis, recurrent aphthous stomatitis, systemic sclerosis, psoriasis, Sjögrens syndrome, Behçet's disease, pruritus, alopecia areata, primary cutaneous marginal zone B-cell lymphomas, vitiligo, chronic prurigo, multiformis, prurigo nodularis, leukocytoclastic vasculitis, prurigo pigmentosa, eczema nummulare, primary cutaneous MALT-type lymphoma, sublamina densa-type linear IgA bullous dermatosis, Sweet's syndrome, cutaneous T-cell pseudolymphoma and pemphigus vulgaris. A critical review of the literature up to May 2017 shows clear evidence of H. pylori involvement only for some of the above purported associations, while in the majority of cases data appear contrasting and/or obtained on a not adequately large study population. Further clinical and laboratory research, with more adequate methodological and statistical basis, is required to assess the actual existence and relevance of many purported associations, as well as the possible role of H. pylori and the underlying pathogenic mechanisms.