Posterior Reversible Encephalopathy Syndrome (PRES) is a life-threatening neurological disease. The aetiology of Addison’s disease has been modified from infectious to autoimmune pathology. Underlying pathogenesis is insufficient production of glucocorticoids and mineralocorticoids. Case series with PRES syndrome and Cushing’s syndrome have been reported but PRESS with adrenal insufficiency is rarely published. We hereby report an operated case of Arnold Chiari malformation presenting with first episode of generalised tonic clonic seizure and diarrhoea for four days. Postictal confusion was present for two hours. She was previously diagnosed with Addison’s disease. Patient had hypotension and dyselectrolytaemia. Systemic examinations were within normal limits. MRI brain revealed features of PRES. The authors encountered certain challenges in her management which included persistent hypokalaemia, hypocalcaemia and hypotension. Patient is on regular follow-up and she is currently asymptomatic. Prompt diagnosis of PRES and intensive case treatment is a must for the betterment of prognosis.