Introduction Filgrastim is a granulocyte colony-stimulating factor (GSCF) used in some chemotherapy regimen to prevent febrile neutropenia. Most common reaction of filgrastim are aches and pain including headaches, nausea and skin rash. Case report We report the case of a patient who developed unusual, non-commonly reported adverse toxidermy to filgrastim. At first the eruption was limited to the lower members and genetics organs. Then it slowly spread across the whole body presenting as a polymorphic exanthematous-pustulosis lesions. Management & Outcome A cutaneous biopsy was done, identifying a toxidermy modified by systemic treatment. A pharmacological study linked the role of filgrastim to these lesions. After switching from filgrastim to lénograstim, his lesions are completely gone and haven't flared up again. Thus, clearly imputing the use of filgrastim. Discussion The cutaneous reaction that has reported with use of GSCF are sweet syndrome, erythema nodosum, pyoderma nodosum and pyoderma gangrenosum. As far as we know, no acute generalized exanthematous pustulosis due to GSCF has been reported.