This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Intravascular heamolysis occurs in 
Select and explain. 
A. Hereditory spherocytosis, B. Antoimmune haemolytic anemia, C. Paroxysmal nocturnal hemoglobinuria, D. Thalassemia
C: Paroxysmal nocturnal hemoglobinuria
Answer: C: Paroxysmal nocturnal hemoglobinuria 
Explanation: 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.