Major Types of Hemoglobin and Its Derivatives

Introduction

Hemoglobin is a crucial protein in red blood cells responsible for oxygen transport. Various hemoglobin variants exist due to genetic mutations or physiological modifications.

Structure of Hemoglobin

Hemoglobin consists of four polypeptide chains (globins) and a heme group that binds oxygen. The primary globin types are alpha, beta, gamma, and delta.

Classification of Hemoglobin Variants

Major Types of Hemoglobin

• Hemoglobin A (HbA): The most abundant form in adults, consisting of α2β2 chains.
• Hemoglobin A2 (HbA2): A minor variant with α2δ2 chains.
• Hemoglobin F (HbF): Fetal hemoglobin with α2γ2 chains, providing higher oxygen affinity.

Abnormal Hemoglobin Variants

• Hemoglobin S (HbS): Responsible for sickle cell disease, altering red cell shape and function.
• Hemoglobin C (HbC): Causes hemoglobin C disease, leading to mild hemolysis.
• Hemoglobin E (HbE): Found commonly in Southeast Asia; linked to mild anemia.

Hemoglobin Derivatives

• Carboxyhemoglobin: Formed by carbon monoxide binding, preventing oxygen transport.
• Methemoglobin: Contains oxidized iron, reducing oxygen delivery.
• Sulfhemoglobin: Formed due to sulfur exposure, impairing oxygen transport.

Clinical Significance

Understanding hemoglobin variants is crucial for diagnosing and managing hemoglobinopathies and related disorders.