**Core Concept**
The peripheral smear of a patient showing hyposegmented neutrophils is indicative of a deficiency in the enzyme glucose-6-phosphate dehydrogenase (G6PD), also known as glucose-6-phosphate dehydrogenase deficiency. This enzyme is crucial for protecting red blood cells from oxidative stress.

**Why the Correct Answer is Right**
G6PD is a key enzyme in the pentose phosphate pathway, which generates NADPH to maintain the reduced state of glutathione in red blood cells. When G6PD is deficient, these cells are more susceptible to oxidative damage, leading to hemolysis. Hyposegmented neutrophils, also known as drumstick or sickle-shaped neutrophils, are a characteristic finding in G6PD deficiency due to the accumulation of Heinz bodies within the neutrophils. The Heinz bodies are aggregates of denatured hemoglobin that form as a result of oxidative damage to the red blood cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not relate to the clinical presentation of hyposegmented neutrophils in peripheral smear.
**Option B:** This option is incorrect as it refers to a different enzyme deficiency (pyruvate kinase deficiency) that presents with a different clinical picture and does not show hyposegmented neutrophils.

**Clinical Pearl / High-Yield Fact**
G6PD deficiency is a common genetic disorder that affects millions of people worldwide, particularly in populations from the Mediterranean, Africa, and Asia. It is essential to be aware of this condition, especially in patients presenting with hemolytic anemia or hemolysis triggered by certain medications or infections.

**Correct Answer:** D.