Evidence based medicine and extradigestive manifestations of Helicobacter pylori.

A putative pathogenetic role has been ascribed to Helicobacter pylori in several extradigestive diseases, including vascular (atherosclerosis and ischaemic heart disease, primary Raynaud phenomenon, primary headache), autoimmune (Sjögren's syndrome, Henoch-Schönlein purpura, autoimmune thyroiditis, idiopathic arrythmias, Parkinson's disease, nonarterial anterior optic ischemic neuropathy), and skin diseases (chronic idiopathic urticaria, rosacea, alopecia areata), sideropenic anemia, growth retardation, late menarche, extragastric MALT lymphoma, diabetes mellitus, hepatic encephalopathy, sudden infant death syndrome, and anorexia of aging. We examine critically the strength of the evidence linking these diseases to Helicobacter pylori, using ischaemic heart disease as an example of epidemiological techniques, and skin diseases as an example of treatment studies. By the standards of evidence-based medicine, studies have been often of low quality. The best evidence usually is not indicative of a role for Helicobacter pylori in these diseases.