The lack of glycosylphosphatidylinositol (GPI)-anchored membrane prote
ins such as decay-accelerating factor (DAF) and CD59 on blood cells ha
s a diagnostic value in paroxysmal nocturnal hemoglobinuria (PNH). Bec
ause PNH often develops in patients with aplastic anemia (AA), we atte
mpted to detect a PNH clone in the bone marrow (BM) of patients with A
A and pancytopenia before affected cells were evident in the periphera
l blood (PB). We used flow cytometry with monoclonal antibodies agains
t DAF and CD59 for the detection of the clone. Affected cells were obs
erved in the BM of 3 of 7 patients with AA and 1 of 3 patients with pa
ncytopenia of unknown origin, but not in their PB. All 8 patients with
apparent PNH had affected cells in their BM and PB. On the basis of t
he early appearance of the PNH clone in the BM, a prospective 4-month
follow-up study of the PB cells was performed, The study showed the re
lease of affected mature cells first in granulocytes, then in monocyte
s, and finally in lymphocytes. Ham's test was positive before affected
erythrocytes were detected by flow cytometry. Our findings indicate t
hat detection of the PNH clone in BM could be predictive of the develo
pment of PNH in patients with AA and pancytopenia. (C) 1995 by The Ame
rican Society of Hematology.