The peripheral blood smear shown above reveals numerous red blood cells with absent central pallor and a spherical shape. This morphology is most characteristic of which of the following conditions?

Explanation

## Image Findings * **Numerous red blood cells (RBCs)** are visible across the field. * A significant proportion of RBCs are **smaller than normal (microcytic)**. * Many RBCs appear **dense and spherical**, lacking the typical biconcave disc shape. * These spherical RBCs exhibit a complete **loss of central pallor**, appearing uniformly stained. ## Diagnosis **Key Point:** The presence of numerous **spherocytes** (small, dense, spherical RBCs with absent central pallor) is the pathognomonic finding for **hereditary spherocytosis**. Hereditary spherocytosis (HS) is the most common inherited disorder of the red blood cell membrane, leading to chronic hemolytic anemia. It is caused by defects in proteins that link the red cell membrane skeleton to the lipid bilayer, such as **spectrin, ankyrin, band 3, or protein 4.2**. These defects result in a loss of membrane surface area, causing the red cells to become spherical and less deformable. Spherocytes are prematurely destroyed in the spleen, leading to extravascular hemolysis. ## Differential Diagnosis | Feature | Hereditary Spherocytosis | Autoimmune Hemolytic Anemia (AIHA) | Iron Deficiency Anemia (IDA) | Thalassemia Major | | :------------------ | :----------------------------------------------------- | :----------------------------------------------------------- | :--------------------------------------------------------- | :----------------------------------------------------------- | | **RBC Morphology** | **Predominant spherocytes**, microcytosis, absent central pallor | Spherocytes (variable), polychromasia, nucleated RBCs, agglutination (Coombs +ve) | Microcytic, hypochromic, **increased central pallor** | Microcytic, hypochromic, target cells, tear-drop cells, nucleated RBCs | | **Etiology** | Inherited RBC membrane protein defect | Autoantibodies against RBCs | Decreased iron stores | Decreased globin chain synthesis | | **Osmotic Fragility** | **Increased** | Increased (variable) | Normal/Decreased | Decreased | | **Coombs Test** | Negative | **Positive** | Negative | Negative | ## Clinical Relevance **Clinical Pearl:** Patients with hereditary spherocytosis typically present with **anemia, jaundice, and splenomegaly**. They are also prone to developing **pigment gallstones** (bilirubin stones) due to chronic hemolysis and **aplastic crises** (often triggered by Parvovirus B19 infection). ## High-Yield for NEET PG **High-Yield:** Hereditary spherocytosis is the **most common inherited cause of hemolytic anemia** in individuals of Northern European descent. The **osmotic fragility test** is a key diagnostic test, showing increased fragility of RBCs in hypotonic solutions. **Key Point:** The **Mean Corpuscular Hemoglobin Concentration (MCHC)** is often elevated in hereditary spherocytosis, which is a distinguishing feature from other microcytic anemias. ## Common Traps **Warning:** Differentiating hereditary spherocytosis from **autoimmune hemolytic anemia (AIHA)** can be challenging as both can present with spherocytes. The key differentiator is the **Coombs test**: negative in HS, positive in AIHA. Also, AIHA often shows more prominent polychromasia and nucleated RBCs, and spherocytes may be less uniform than in HS. ## Reference [cite:Robbins Basic Pathology, 10th Edition, Chapter 13, Red Blood Cell and Bleeding Disorders] [cite:Harrison's Principles of Internal Medicine, 20th Edition, Chapter 107, Hemolytic Anemias]