In this context, it has to be noted that two GPI-anchor synthesis defects, paroxysmal nocturnal haemoglobinuria (PNH), and PIGM-CDG (Figure 1), exhibit a high rate of occurrence of severe thrombotic events due to complement-mediated hemolysis resulting from the deficiency of complement regulatory proteins, CD55 and CD59 [12,13]. Here, CD55 is linked to paroxysmal nocturnal hemoglobinuria.