Introduction: High-dose glucocorticosteroids (GC) are the treatment of choice for acute relapses in patients with multiple sclerosis as proven by several controlled clinical trials. The common adverse effects of GC are well known Case Presentation: In this study, we report on the exceptional case of a young female treated with intravenous high-dose prednisolone for optic neuritis who developed acute generalized exanthematous pustulosis (AGEP). AGEP is a rare cutaneous adverse reaction induced most frequently by antimicrobial or antihypertensive drugs and viral infections. It is characterized by a febrile erythematous and pustular rash and blood granulocytosis. Conclusion: In our patient, switching to dexamethasone for the next relapse was tolerated well and is an option for treatment. AGEP is a rare adverse effect of carticosteroid treatment.