Differential diagnosis of skin lesions after allogeneic haematopoietic stem cell transplantation.

Allogeneic haematopoietic stem cell transplantation (i.e. bone marrow or peripheral blood stem cell transplantation) is a common procedure in the treatment of various haematological disorders such as aplastic anaemia, (pre)leukaemias, some malignant lymphomas, multiple myeloma and immunodeficiency states. Many of these patients develop erythematous skin lesions following transplantation. Although graft- versus-host disease is the major differential diagnosis in these situations, many other causes of erythema are encountered. The large number of transplant patients means that more and more pathologists are confronted with the challenging problem of making a correct diagnosis in these situations. In this review article we therefore describe the different causes of erythema and their differential diagnoses. In most cases the clinical presentation is related to the microscopical features. Besides acute and chronic graft-versus-host disease, we discuss the (common) drug reactions and non-specific features such as Sweet's syndrome, erythema nodosum and eosinophilic folliculitis. In addition, we deal with the recurrence of original diseases and infections. With this knowledge every pathologist should feel comfortable when looking at skin biopsies of patients after haematological stem cell transplantation.