Thrombotic thrombocytopenic purpura (TTP) is a multisystem disorder characterized by a pentad consisting of thrombocytopenic, microangiopathic hemolytic anemia, renal dysfunction, neurological signs and fever. Coexistence of thrombotic thrombocytopenic purpura and Adult Onset Still's Disease (AOSD) is extremely rare. We report a case of 18 year old girl with AOSD who developed TTP. Neuroimaging of brain demonstrated white matter edema consistent with reversible posterior leukoencephalopathy syndrome (RPLS). Complete recovery occurred with prompt anti-hypertensive treatment and high dose immunoglobulin infusions (IVIg). Plasma exchange is the standard of care and the first line treatment for patient with TTP. We used IVIg alone in our case and this showed a gratifying response. Use of IVIG before considering plasmapharesis is justifiable or not requires randomized control clinical trials. This should determine the optimal therapeutic strategies for TTP.