A 38-year-old woman from rural Maharashtra presents with progressive fatigue, dyspnea on exertion, and jaundice for 3 weeks. She has a history of recurrent episodes of similar symptoms over the past 2 years, each lasting 1–2 weeks and self-resolving. On examination: pallor, mild splenomegaly, no lymphadenopathy. Labs: Hb 7.2 g/dL, reticulocyte count 12%, total bilirubin 4.8 mg/dL (indirect 4.2), LDH 680 U/L, haptoglobin <10 mg/dL. Peripheral blood smear shows spherocytes, polychromasia, and occasional bite cells. Direct Coombs test is negative. What is the most likely diagnosis?

Explanation

## Clinical Presentation & Key Findings **Key Point:** The combination of spherocytes on smear, negative Direct Coombs test, recurrent self-limited hemolytic episodes, and splenomegaly in a young woman is classic for **Hereditary Spherocytosis (HS) presenting with an acute hemolytic crisis**. ## Why Hereditary Spherocytosis (HS)? The clinical and laboratory features that point to HS: - **Spherocytes as the primary finding** — in HS, spherocytes are the dominant and primary smear finding due to membrane protein defects (spectrin, ankyrin, band 3) - **Negative Direct Coombs test** — excludes autoimmune hemolytic anemia (AIHA) - **Recurrent episodic hemolysis** — HS patients have chronic compensated hemolysis with episodic crises triggered by infections (aplastic crisis from Parvovirus B19, or hemolytic crisis from other infections) - **Splenomegaly** — characteristic of HS due to chronic splenic trapping of spherocytes - **Reticulocytosis (12%)** — reflects brisk compensatory erythropoiesis - **Elevated indirect bilirubin and LDH, low haptoglobin** — markers of hemolysis ## Why NOT G6PD Deficiency? While bite cells are mentioned as "occasional," the **dominant smear finding is spherocytes**, which is not the hallmark of G6PD deficiency. In G6PD deficiency: - Bite cells (blister cells) are the **primary and pathognomonic** finding - Spherocytes are secondary and less prominent - Episodes are triggered by specific oxidative stressors (drugs, fava beans, infections) and are typically more acute and severe - G6PD deficiency is **X-linked recessive** — symptomatic disease in females requires homozygosity or skewed X-inactivation, making it less common in women - The **recurrent, self-resolving pattern over 2 years** with splenomegaly is more consistent with HS ## Differential Diagnosis Table | Feature | Hereditary Spherocytosis | G6PD Deficiency | Autoimmune HA | Thalassemia Major | |---|---|---|---|---| | **Coombs Test** | Negative | Negative | **Positive** | Negative | | **Primary Smear Finding** | **Spherocytes** | Bite cells | Spherocytes | Target cells, nucleated RBCs | | **Splenomegaly** | **Prominent** | Mild/absent | Variable | Massive | | **Sex predilection** | None | Males >> Females | None | None | | **Trigger** | Infections (aplastic/hemolytic crisis) | Oxidative stress | Autoimmune | Genetic (presents in infancy) | | **Chronicity** | Chronic + episodic crises | Acute episodic | Variable | Lifelong from infancy | ## Mechanism of Spherocyte Formation in HS ``` Membrane protein defect (spectrin/ankyrin/band 3 mutation) → Loss of membrane lipid bilayer → Reduced surface area-to-volume ratio → Spherocyte formation → Splenic trapping and hemolysis ``` **Clinical Pearl:** HS is the most common inherited hemolytic anemia in Northern Europeans but is also well-documented in Indian populations. Acute hemolytic crises in HS are commonly precipitated by infections (including malaria, common in rural Maharashtra), making this presentation highly consistent. Splenectomy is curative. [cite: Robbins & Cotran Pathologic Basis of Disease, 10e, Ch 14; Harrison's Principles of Internal Medicine, 21e, Ch 99]