Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired haemopoietic stem cell disorder
arising from somatic mutation of the X-linked PIG-A gene which leads to deficiency of the
glycosylphosphatidylinositol (GP1) membrane anchor proteins such as CD 59 (MIRL: membrane
inhibitor of reactive lysis) and CD 55 (DAF: decay accelerating factor). Allogeneic peripheral
blood stem cell transplant (PBSCT) is a curative mode of treatment in symptomatic PNH patients.
Assessment of donor chimerism for PBSCT can be performed by various methods including short
tandem repeat loci (STR) and variable number of tandem repeats (VNTR). Flow cytometry, which
is much cheaper and faster, also can be used to assess engraftment in patients with PNH. Engrafted
patients will show the presence of CD 55 and CD 59 on their red cells and white cells. We describe
here the usefulness of flow cytometry in the assessment of donor chimerism following allogeneic
PBSCT, in a case of PNH.