- Given clinical features suggests the diagnosis of PNH - Despite its name, the disorder is nocturnal in only a minority of cases. - PNH is a clonal stem cell disorder characterized by episodic intravascular hemolytic anemia; secondary to increased sensitivity of erythrocytes to complement-mediated lysis. - It is d/t somatic mutation of phosphatidylinositol glycan-class A (PIG-A) gene. - Most useful diagnostic test is flow cytofluorometry. - other tests used are: Sucrose hemolysis test Acidified serum (Ham test) - Choices B and C are hemolytic conditions, do not show increased lysis in described laboratory studies.