A patient presents with intravascular hemolysis, pancytopenia, venous thrombosis, and morning hemoglobinuria. What is suspected?

A patient presents with intravascular hemolysis, pancytopenia, venous thrombosis, and morning hemoglobinuria. What is suspected?

• A. Glucose-6-phosphate dehydrogenase deficiency
• B. Paroxysmal nocturnal hemoglobinuria
• C. Cold agglutinin disease
• D. Sickle cell disease

Answer: (B)

This pattern points to paroxysmal nocturnal hemoglobinuria. The underlying issue is a clonal defect in hematopoietic stem cells that leads to loss of GPI-anchored proteins such as CD55 (DAF) and CD59 on red cells, white cells, and platelets. Without these protective proteins, blood cells become highly susceptible to complement-mediated lysis, especially during sleep when slight acidosis can augment complement activity. The result is intravascular hemolysis that releases free hemoglobin, often presenting as hemoglobinuria in the morning. Because the abnormal clone arises in a stem cell, multiple blood cell lineages can be affected, giving pancytopenia in some patients. The combination of intravascular hemolysis, pancytopenia, and a tendency toward venous thrombosis is characteristic, with thrombosis being a leading cause of morbidity and mortality in PNH. Morning hemoglobinuria is a classic clue due to the nocturnal hemolysis that becomes noticeable upon waking. Diagnostic confirmation is typically by flow cytometry showing loss of GPI-anchored proteins (CD55 and CD59) on blood cells; historically, the Ham test could be supportive but is less used now. Other conditions don’t fit this combination as well. Glucose-6-phosphate dehydrogenase deficiency causes episodic oxidative hemolysis but not the pancytopenia and high risk of venous thrombosis seen here. Cold agglutinin disease involves IgM-mediated autoimmune hemolysis with cold-induced symptoms and does not typically produce pancytopenia or morning hemoglobinuria. Sickle cell disease can cause hemolysis and thrombosis but lacks the characteristic morning hemoglobinuria and the pancytopenic pattern driven by a single clone with loss of GPI anchors.

This pattern points to paroxysmal nocturnal hemoglobinuria. The underlying issue is a clonal defect in hematopoietic stem cells that leads to loss of GPI-anchored proteins such as CD55 (DAF) and CD59 on red cells, white cells, and platelets. Without these protective proteins, blood cells become highly susceptible to complement-mediated lysis, especially during sleep when slight acidosis can augment complement activity. The result is intravascular hemolysis that releases free hemoglobin, often presenting as hemoglobinuria in the morning.

Because the abnormal clone arises in a stem cell, multiple blood cell lineages can be affected, giving pancytopenia in some patients. The combination of intravascular hemolysis, pancytopenia, and a tendency toward venous thrombosis is characteristic, with thrombosis being a leading cause of morbidity and mortality in PNH. Morning hemoglobinuria is a classic clue due to the nocturnal hemolysis that becomes noticeable upon waking.

Diagnostic confirmation is typically by flow cytometry showing loss of GPI-anchored proteins (CD55 and CD59) on blood cells; historically, the Ham test could be supportive but is less used now.

Other conditions don’t fit this combination as well. Glucose-6-phosphate dehydrogenase deficiency causes episodic oxidative hemolysis but not the pancytopenia and high risk of venous thrombosis seen here. Cold agglutinin disease involves IgM-mediated autoimmune hemolysis with cold-induced symptoms and does not typically produce pancytopenia or morning hemoglobinuria. Sickle cell disease can cause hemolysis and thrombosis but lacks the characteristic morning hemoglobinuria and the pancytopenic pattern driven by a single clone with loss of GPI anchors.