Immune thrombocytopenic purpura (ITP) and Helicobacter pylori

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by antibody destruction of platelets. Symptoms include abnormal bruising and petechiae (small red or purple dots due to capillary hemorrhage). More serious mucosal or intracranial bleeding can occur in a subset of cases. ITP, like so many other autoimmune conditions, emerges after the immune system is triggered by an infectious disease. A study just published in the journal Helicobacter reports on spontaneous resolution of ITP symptoms in a large percentage of patients after eradication of the common gastrointestinal pathogen Helicobacter pylori. The authors state:

"Since a report by Gasbarrini et al. in 1998, an accumulating body of evidence has proposed a pathophysiological link between ITP and chronic Helicobacter pylori (H. pylori) infection. Clinical reports have described a spontaneous resolution of ITP symptoms in about 50% of chronic ITP patients following empirical treatment of H. pylori infection, but response appears to be geography dependent."

The H. pylori-specific cytotoxic-associated gene A (CagA)

They explore the relationship between 'genetic geography' and susceptibility to ITP by observing loss of immune tolerance for an H. pylori gene:

"Studies have also documented that ITP patients in East Asian countries are more likely to express positive antibody titers against H. pylori-specific cytotoxic-associated gene A (CagA), a virulence factor that is associated with an increased risk for gastric diseases including carcinoma. "

Role of molecular mimicry

Molecular mimicry fundamental mechanism of loss of immune tolerance for self-antigens when the immune system cross-reacts to 'similar looking targets' as it attacks pathogens and foreign materials.

"While a definitive mechanism by which H. pylori may induce thrombocytopenia remains elusive, proposed pathways include molecular mimicry of CagA by host autoantibodies against platelet surface glycoproteins, as well as perturbations in the phagocytic activity of monocytes."

Potential for ITP therapy

Case management of autoimmune disorders includes clearance of chronic infections, and treatment of infection requires vigilance in preventing or detecting autoimmune sequelae. With ITP clinicians should bear in mind the need to check for H. pylori infection:

"Traditional treatments of ITP have been largely empirical, involving the use of immunosuppressive agents and immunoglobulin therapy. However, based on the findings of clinical reports emerging over the past 20 years, health organizations around the world increasingly suggest the detection and eradication of H. pylori as a treatment for ITP."