Milkers' nodules complicated by erythema multiforme and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation for multiple myeloma.

We describe a case of cow-transmitted parapoxvirus infection--also known as milkers' nodules--after a hematopoietic stem cell transplantation for multiple myeloma. The infection was complicated by erythema multiforme and acute exacerbation of graft-versus-host disease. Parapoxvirus was confirmed by electron microscopy. The natural history of milker's nodules in immunocompetent hosts is described and compared to that in our immunocompromised patient.