A 39-year-old man reports seeing red-colored urine in the morning. The CBC reveals anemia, low serum iron, and an elevated reticulocyte count. Laboratory studies show increased lysis of erythrocytes when incubated with either sucrose or acidified serum. Which of the following is the appropriate diagnosis?
Anemia of chronic renal failure
Microangiopathic hemolytic anemia
Paroxysmal nocturnal hemoglobinuria
Answer : D Paroxysmal nocturnal hemoglobinuria
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 that is secondary to increased sensitivity of erythrocytes to complement- mediated lysis.
The underlying defect involves somatic mutation of the phosphatidylinositol glycan-class A (PIG-A) gene.
PNH may develop as a primary disorder or evolve from preexisting cases of aplastic anemia. During hemolytic episodes, patients develop normocytic or macrocytic anemia, accompanied by an appropriate reticulocyte response.
The traditional diagnostic tests for PNH, hemolysis in sucrose (sucrose hemolysis test) or acidified serum (Ham test), are now more easily diagnosed by demonstrating loss of GPI-anchored proteins on blood cells by flow cytometry which are hemolytic conditions, do not show increased lysis in the described laboratory studies.