Rituximab is a plausible alternative first-line treatment of ANCA-associated vasculitis. Adverse effects related to its infusion are common and usually have a benign course. However, there have been reports of refractory cardiogenic shock simulating septic shock. We report an 81 years male with the diagnosis of ANCA associated vasculitis. Rituximab 500 mg was administered intravenously for a relapse. The infusion proceeded without incident. However, 24 hours after its administration the patient began with fever, chills, coughing and strong malaise. The patient was transferred to the critical patient unit where a septic shock was suspected and resuscitative measures were started. However, the fast response to moderate doses of vasoactive drugs and complementary tests did not support an infectious etiology for the shock. Antimicrobials were discontinued and systemic corticosteroids were maintained, achieving remission of the symptoms. Shock as an unusual adverse reaction to Rituximab was suspected.Rituximab is a plausible alternative first-line treatment of ANCA-associated vasculitis. Adverse effects related to its infusion are common and usually have a benign course. However, there have been reports of refractory cardiogenic shock simulating septic shock. We report an 81 years male with the diagnosis of ANCA associated vasculitis. Rituximab 500 mg was administered intravenously for a relapse. The infusion proceeded without incident. However, 24 hours after its administration the patient began with fever, chills, coughing and strong malaise. The patient was transferred to the critical patient unit where a septic shock was suspected and resuscitative measures were started. However, the fast response to moderate doses of vasoactive drugs and complementary tests did not support an infectious etiology for the shock. Antimicrobials were discontinued and systemic corticosteroids were maintained, achieving remission of the symptoms. Shock as an unusual adverse reaction to Rituximab was suspected.