A 32 -year-old female is found on routine physical examination to have splenomegaly. She reports no acu te change in her energy levels. However. she does note bei ng more easily fatigued duri ng heavy physical activity as long as she can remember. Patien t re-ports a h istory of cholelithiasis diagnosed 1 0 years previously; however. she elected not to undergo cholecystectomy. Mild splenomegaly is noted on physical examination . Laboratory workup reveals hemoglobin 11 .2 g/dl. mean corpuscular volume (MCV) 85 fl. leu kocyte count 6.500/,LLL. and platelet count of 361 . 000/,LLL. I ndirect bil irubin level ismini mall el vated and tneoireccanriglooin--resns negative. -reriph-eraJ-blood· smear is shown below.
What is the underlying molecular defect in hereditary spherocytosis?
- Defects in the vertical interactions between membrane skeleton and the lipid bilayer
- Defects in the horizontal interactions between membrane skeleton and the lipid bilayer
- Defective ion transport across red blood cell membrane
- Defective ability to neutralize oxidative stress
- Abnormal hemoglobin polymers causing red blood cell membrane damage
Medicine
A. Hereditary spherocytosis is caused by defects in the vertical interactions between mem-brane skeleton and the lipid bilayer secondary to functional deficiency or absence of spectrin, ankyrin, protein 4.2, and band 3. Hereditary elliptocytosis is caused by defects in the horizontal interactions.
Hereditary spherocytosis classically presents as a mild to moderate hemolytic anemia with variable degrees of splenomegaly (Br J Haematol. 1999;104(1):2).
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