Sweet's syndrome associated with granulocyte colony-stimulating factor

We present two patients who developed Sweet's syndrome (SS) during recombinant granulocyte colony-stimulating factor (G-CSF) treatment, Case 1: on day 11 of the fifth cycle of G-CSF treatment, a 21-year-old man with relapsed, intracranial germ cell tumor had fever, and painful, subcutaneous nodules on his right arm and right leg concomitant with neutrophilia, Skin biopsy revealed neutrophilic panniculitis, The skin lesions disappeared completely after discontinuance of G-CSF. Case 2 : on day 7 of G-CSF treatment, a 50-year-old woman with small cell lung cancer developed fever, and widely disseminated pruritic erythema on her trunk and extremities. The histopathology of the skin was compatible with SS, Her skin lesions also disappeared after discontinuance of G-CSF treatment. She subsequently received three cycles of additional G-CSF treatments without recurrence of SS, It is possible that G-CSF treatment accidentally induced or augmented the proliferation and differentiation of clonal neutrophils with abnormal functions, since in the cases presented SS developed only once in spite of several treatments with G-CSF.