Chronic immune thrombocytopenia in adults: epidemiology and clinical presentation.

Data concerning the prevalence of chronic immune thrombocytopenia (ITP) among adults are limited and are confounded by lack of concordance of definitions of stage of disease. In the largest series of outpatients, prevalence has been estimated to range from 5.6 to 20 per 100,000 population and increases with advancing age. A female predominance is most pronounced among middle-aged patients, and no racial variation is apparent. Adult patients with chronic ITP may have a better prognosis than previously thought, although bleeding risk increases dramatically in association with severe thrombocytopenia and older age; a small minority of patients may recover spontaneously. More systematic analyses, with standardized definitions of cases and adequate duration of follow up, are needed.