A patient presents with normocytic anemia, and further investigation reveals a reduced level of haptoglobin and an increased level of lactate dehydrogenase (LDH). What is the most likely diagnosis?

A Autoimmune hemolytic anemia
B Hereditary spherocytosis
C Paroxysmal nocturnal hemoglobinuria (PNH) ✓
D Hemolytic uremic syndrome (HUS)

Explanation

The combination of normocytic anemia, low haptoglobin, and high LDH suggests intravascular hemolysis. PNH is a rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells (hemolysis), bone marrow failure, and the potential for blood clot formation (thrombosis).

Source

Wintrobe's Clinical Hematology
Hematology Hematology: Anemia Hematology: Anemia Medium MEDICAL Confidence: high