Pathology - Hereditary Spherocytosis
Hereditary spherocytosis (HS) resulting in the development of calcium bilirubinate (pigment) gallstones and subsequent choledocholithiasis. HS is an autosomal dominant condition resulting in defective proteins (e.g., ankyrin, band 3.1, spectrin) that interact with the RBC skeleton and plasma membrane. Decreased membrane contact leads to small, spherical RBCs with no central pallor (spherocytes). The membrane defect and defective Na+/K+-ATPase pump results in increased permeability to sodium (positive osmotic fragility test as mentioned in the vignette). Extravascular hemolysis of the aberrant cells results in jaundice, splenomegaly, and high indirect (unconjugated) bilirubin levels. Excess bilirubin in bile contributes to production of calcium bilirubinate (black pigment) gallstones. In this example, gallstones have become lodged in the CBD (choledocholithiasis) generating high direct (conjugated) bilirubin and elevated alkaline phosphatase. As the patient is afebrile with negative Murphy’s sign and absent leukocytosis, cholangitis is not anticipated and elective removal of the gallbladder is advised to prevent recurrence and complications. Vaccination for encapsulated organisms is also indicated in patients with autosplenectomy.
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