MCQ Hematology Answer 3

1. Paroxysmal nocturnal haemoglobinuria , an acquired clonal blood disorder, is caused by the absence of glycosyl phosphatidylinositol (GPI)-anchored surface proteins due to a defect in a specific step of GPI-anchor synthesis
   
2. A molecule called PIGA (phosphatidylinositol glycan A) is needed to make a cell membrane anchor for proteins called GPI (glycosylphosphatidylinositol).
   
3. The gene that codes for PIGA is inherited in an X-linked fashion, which means that only one active copy of the gene for PIGA may exist. If a mutation occurs in this gene then PIGA may be defective, which leads to a defect in the GPI anchor.
   
4. When this mutation occurs in a bone marrow stem cell (which are used to make red blood cells as well as white blood cells and platelets), all of the cells it produces will also have the defect.
5. Several of the proteins that anchor to GPI on the cell membrane are used to protect the cell from destruction by the complement system.
   
6. The complement system is part of the immune system and helps to destroy invading microorganisms. Without the proteins that protect them from complement, red blood cells are destroyed.
   
7. The main proteins which carry out this function are CD16, CD55 and CD59

Category: Hematology MCQs