GATA2 is a transcription factor that is involved in the lympho-hematopoiesis. Mutations of GATA2 cause MonoMAC syndrome (monocytopenia and mycobacterial infections)/DCML deficiency (dendritic cell, monocyte, B and natural killer (NK) lymphoid deficiency), Emberger syndrome (lymphoedema with MDS), and MDS/AML. In this review, we explain the new function of GATA2, and describe the clinical phenotypes, laboratory findings, pathology, genetic anomalies and etiology.