Bortezomib-induced histiocytoid Sweet syndrome.

Bortezomib, a proteasome inhibitor approved for the treatment of multiple myeloma, has been reported to be associated with Sweet syndrome. However, careful review of the histopathology of the first reported case and our case revealed similar histologic and immunohistochemical findings (a mononuclear dermal infiltrate) and not the usual neutrophilic infiltrate of Sweet syndrome. We suggest that the dermatitis induced by bortezomib is best classified as "histiocytoid Sweet syndrome.