Effectiveness of tocilizumab for IgA vasculitis associated with idiopathic multicentric Castleman's disease: Two cases and literature review.

Idiopathic multicentric Castleman's disease (iMCD) is a systemic lymphoproliferative disorder characterised by interleukin (IL)-6 overproduction. To date, several cases of iMCD with autoimmune features have been reported, and cases of iMCD complicated by IgA vasculitis have also been reported. IL-6 is reported to promote the production of galactose-deficient IgA1, a key pathogenic factor in IgA vasculitis. Therefore, IL-6 overproduction in iMCD may contribute to the development of IgA vasculitis in these cases. Here, we present two cases of iMCD complicated by IgA vasculitis, both successfully treated with tocilizumab, an IL-6 receptor blockade. Furthermore, our literature review identified two reported cases of iMCD complicated by IgA nephropathy, and one case of iMCD complicated by IgA vasculitis, all of which responded favourably to tocilizumab. Our cases and literature review suggest the pathogenic role of IL-6 in the development of IgA vasculitis in iMCD and the effectiveness of tocilizumab as a potential therapeutic option not only for iMCD itself, but also for IgA vasculitis in the setting of iMCD.