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Hereditary Spherocytosis (HS)

  1. An autosomal dominant disorder. 
  2. There is a qualitative and quantitative deficiency of vital skeletal proteins of RBC membrane namely spectrin, ankyrin (most common) and band 3. Paladin (protein 4.2).
  3. Loss of normal spectrin of RBC membrane results in loss of lipids from the membrane leading to loss of surface area and altered RBC morphology. 
  4. RBCs lose their normal biconcave shape and become spherocytic with a decrease in surface to volume ratio.
Extra Edge (Ref. Hari. 18th ed., Pg- 874)
  1. The most abundant of these proteins are glycophorin and the so-called band 3, an anion transporter. 
  2. The extracellular domains of many of these proteins are heavily glycosylated, and they carry antigenic determinants that correspond to blood groups. 
  3. Underneath the membrane, and tangential to it, is a network of other proteins that make up the cytoskeleton: the main cytoskeletal protein is spectrin, the basic unit of which is a dimer of -spectrin and -spectrin. 
  4. The membrane is physically linked to the cytoskeleton by a third set of proteins (including ankyrin and the so-called band 4.1 and band 4.2), which thus make these two structures intimately connected to each other.


Important Points

Membrane Protein defect - Ankyrin > Protein 3 > spectrin > Band 3 > Paladin


Clinical Features
  1. Mild anemia (Hb 8 –12 gm/dl),
  2. Splenomegaly,
  3. Pigment gallstones, 
  4. Jaundice,
  5. Growth retardation,
  6. Leg ulcer.
  1. Presence of hemolytic state., MCV ↓, MCHC ↑
  2. Increased osmotic fragility of RBCs:
  3. Presence of spherocytes in the blood film

Extra Edge (Ref. Hari. 18th ed., Pg- 875)

  1. A characteristic feature is an increase in MCHC: this is the only condition in which an increased MCHC is seen.
  2. In most cases, the diagnosis can be made on the basis of red cell morphology and of a test for osmotic fragility, a modified version of which is called the "pink test."
  1. Causes of increased osmotic fragility
    1. H. spherocytosis
    2. Autoimmune hemolytic anaemia
    3. Hemolytic disease of new born
    4. Malaria
    5. Severe PK deficiency
  2. Causes of Decreased osmotic fragility is seen in:
    1. Sickle cell disease
    2. Thalassemia
Complication: Sudden fall in Hb
  1. Hemolytic crisis (There is increase reticulocyte count)
  2. Aplastic crisis = Parvo virus (Retic count is reduced)
Treatment of choice is do Splenectomy after 14 – 15 years of age
  1. Splenectomy: This is indicated
    1. When anemia causes health impairment
    2. Hemolytic
    3. Aplastic crises (Percolated by Parvovirus infection)
    4. Evidence of cholecystitis and cholelithiasis is present
      Pneumococcal vaccine should be given 1 –2 months prior to splenectomy. 
  2. Daily penicillin V, 250 mg 12 hourly is prescribed for at least 5 years following splenectomy.
  3. Blood transfusion in severe hemolytic crises. 
  4. Folic acid 5 mg per day orally is prescribed to support the increased erythropoiesis
Important Points:

Remember the following also:

  1. Hereditary spherocytosis is inherited as : Autosomal dominant
  2. Most important protein in RBC membrane : Spectrin
  3. In HS, Most common membrane defect is that of : Ankyrin (Robbins 7th edition 625)
  4. One characteristic clinical presentation is : Striking splenomegaly (Anemia, splenomegaly, jaundice)
  5. Treatment of choice (in older children) : Splenectomy

Causes of spherocytosis in peripheral smear

  1. Hereditary spherocytosis
  2. Immunohemolytic anemias (Autoimmune hemolytic anemias)
  3. In association with hemolysis induced by splenomegaly in patients with cirrhosis
  4. Clostridial infections
  5. Certain snake envenomations
  6. G6PD deficiency (Few spherocytes)

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