Paroxysmal nocturnal hemoglobinuria (APG) is a rare clonal disease, an acquired form of hemolytic anemia from the group of rare (orphan) diseases. A characteristic clinical manifestation with a significant APG clone (usually more than 10 % of the total number of blood cells) is chronic intravascular hemolysis, which, with its high activity, leads to the development of anemia, an increased tendency to thrombosis and a number of organ disorders. Manifestations of bone marrow insufficiency of varying degrees are also typical for APG, and in some cases association with aplastic anemia, less often with myelodysplastic syndrome and other hematological diseases with cerebral insufficiency. This article describes a rare clinical case of orphan disease – paroxysmal nocturnal hemoglobinuria (APG) in association with aplastic anemia.