Paroxysmal nocturnal hemoglobinuria (PNH) is a disease that results from defects in:

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease that results from acquired mutations in the phosphatidylinositol glycan complementation group A gene (PIGA), an enzyme that is essential for the synthesis of ceain cell surface proteins. Proteins are anchored into the lipid bilayer in two ways. Most have a hydrophobic region that spans the cell membrane; these are called transmembrane proteins. The others are attached to the cell membrane through a covalent linkage to a specialized phospholipid called glycosylphosphatidylinositol (GPI). In PNH, these GPI-linked proteins are deficient because of somatic mutations that inactivate PIGA. Ref: Robbins 8th edition Chapter 14.