Adrenal insufficiency is a rare disease, but is life threatening when overlooked. Addison's disease may be an acquired form of adrenal insufficiency due to the destruction or dysfunction of the adrenal cortex. It affects both glucocorticoid and mineralocorticoid function. Main presenting symptoms of Addison's disease such as fatigue, anorexia, vomiting and convulsion often mimics central nervous system (CNS) infections. We describe a case of Addison's disease who was initially misdiagnosed as a case of meningo-encephalitis subsequently renal tubular acidosis and finally Addison's disease. Addison's disease can remain unrecognized until acute crisis and sometimes it may be misdiagnosed.