<prompt> Intravascular heamolysis occurs inHereditory spherocytosisAntoimmune haemolytic anemiaParoxysmal nocturnal hemoglobinuriaThalassemia  <response>: Paroxysmal noctural hemoglobunuria PNH is the only hemolytic anemia caused by an acquired intrinsic defect in the cell membrane. It is associated with intravascular hemolysis. Rest all conditions causes extravascular heamolysis. 