We hereby describe a case of an acutely ill 41-year-old male without any medical history who presented with an acute abdomen in the emergency department. An abdominal CT showed a dissection of the coeliac trunk and infarction of the spleen. Because of a presumed diagnosis of vasculitis he was started on high dose IV steroids. However, after additional testing the diagnosis of segmental arteriolar Mediolysis (SAM) was made. In this case report we describe the presentation, diagnosis, treatment and follow-up of this patient and provide the readers with background about common differential diagnosis and criteria for diagnosing SAM.