Review Question - QID 212689

This patient with shortness of breath, fatigue, neonatal jaundice, and echinocytes on peripheral blood smear most likely has pyruvate kinase deficiency, which would present with increased lactate dehydrogenase.

Pyruvate kinase deficiency is an autosomal recessive cause of intrinsic hemolytic anemia due to a mutation in this component of glycolysis. Since red blood cells lack mitochondria, they rely upon glycolysis as their main source of energy production. Patients with pyruvate kinase deficiency cannot generate adequate energy reserves to power the sodium-potassium pump, which over time results in cellular swelling. The swollen red blood cells are recognized and cleared by macrophages in the spleen. This disease can present with neonatal jaundice and anemia later in life.

Figure/Illustration A shows swollen red blood cells with protruding spines known as echinocytes. These echinocytes are indicated by black circles and are characteristically seen in pyruvate kinase deficiency.

Incorrect Answers:
Answer 1: Increased haptoglobin would not be seen. Rather, you would see a decreased haptoglobin level due to hemolysis in pyruvate kinase deficiency.

Answer 2: Decreased mean corpuscular volume would be seen in causes of microcytic anemia such as lead poisoning; however, the echinocytes seen in this patient are more suggestive of pyruvate kinase deficiency, which is a normocytic anemia.

Answer 3: Increased hematocrit would be seen in cases of polycythemia; however, this patient's presentation is more consistent with anemia rather than polycythemia.

Answer 5: Increased mean corpuscular volume would be seen in causes of macrocytic anemia such as vitamin B12 or folate deficiency; however, these disorders would present with hypersegmented neutrophils rather than echinocytes on peripheral blood smear. Pyruvate kinase deficiency leads to a normocytic anemia.

Bullet Summary:
Pyruvate kinase deficiency presents with normocytic red blood cells and echinocytes.