Purpose of review: To review the current knowledge of epidemiological features of immunoglobulin (Ig) A vasculitis (Henoch-Schönlein) and disease etiology.
Recent findings: The annual incidence of IgA vasculitis in the population is an estimated 3-26.7/100 000 for children and infants and 0.8-1.8/100 000 for adults. These may be conservative approximations of the true frequency because of skewed case-finding strategies. In children, the marked autumn-winter peak in incidence rates, the frequent occurrence after an upper respiratory tract infection and the short interval between disease onset in index cases and in other family members collectively point to a transmissible infectious process. A subset of adult IgA vasculitis could be related to preceding or concurrent malignancies. Despite several lines of evidence supporting the critical role of an exogenous factor in IgA vasculitis, recent progress has been made in understanding the genetic susceptibility to IgA vasculitis. Recent findings also lessened the suggestion that IgA vasculitis might be triggered by vaccination.
Summary: IgA vasculitis is two to 33 times more common in children than adults and appears to have a strong environmental component, with possibly different risk factors in childhood and adulthood. Support is strengthening for a role of genetics in IgA vasculitis.