This book discusses the severe chronic disease of Sarcoidosis. Even though Sir Jonathan Hutchinson explained sarcoid lesions more than a century ago but the cause of this granulomatous disease is still unrecognized. While many patients affected by this disease enter spontaneous remission, some patients relapse after intervention or get chronically affected which remains an unexplained characteristic of sarcoidosis. This book highlights advances and recent developments in the ongoing researches on sarcoidosis which contribute to our understanding of the complex nature of this disorder. It presents a variety of topics including a recent approach of etiology as an endogenous infection caused due to hypersensitivity to indigenous bacteria, new directions in therapy, new diagnostic approaches with FDG-PET and EBUS-TBNA, and latest immunopathogenesis and genetic factors. This book will assist the readers in their practice and researches of sarcoidosis.