The following protein defects can cause hereditary spherocytosis except: (AIPG 09)
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 glycophorins and band 3.
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.
Membrane Protein defect - Ankyrin > Protein 3 > spectrin > Band 3 > Paladin
1. Mild anemia (Hb 8 –12 gm/dl),
3. Pigment gallstones,
5. Growth retardation,
6. Leg ulcer.