Eosinophilic folliculitis: an important differential diagnosis after allogeneic bone-marrow transplant

Eosinophilic folliculitis (EF) is a descriptive histopathological term applied to a heterogeneous group of disorders. In EF, the characteristic histopathological features are eosinophilic spongiosis and pustulosis involving the infundibular region of the hair follicle. EF may be seen in association with bacterial and fungal infection, drug reactions and haematological disorders. However, in those conditions, the histopathological changes are rarely restricted to the infundibula but in most cases include a moderate to dense perifollicular or even diffuse dermal infiltrate of lymphocytes, or eosinophilic or neutrophilic granulocytes. We present two cases of EF after mini-allogeneic bone-marrow transplantation (BMT) in order to highlight this rare and perhaps under-recognized clinical association.