The acquired bone marrow failure (BMF) syndromes include aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and myelodysplastic syndromes (MDS). In this study, to clarify what the frequencies of borderline PNH patients with lower proportions of glycosylphosphatidylinositol (GPI)-deficient erythrocytes and no apparent clinical symptoms of PNH, such as visible hemoglobinuria, are and the significance of serum haptoglobin (Hpl) in patients with BMF, we investigated flow cytometry of erythrocytes and granulocytes with expression of CD59 and quantified serum Hpl in 142 Japanese patients with BMF, including 54 AA, 36 PNH, and 52 MDS patients. The diagnosis and grading of the severity of AA were based on the criteria of the International Agranulocytosis and Aplastic Anemia Study Group and that of Frickhoten et al, respectively. A patient with over 1% of CD59 erythrocytes was judged to have PNH erythrocytes. The diagnosis and phenotypes of MDS were determined according to the French-American-British criteria. The concentrations of serum Hpl were measured by the nephelometric procedure, developed by Van Lente et al, with some modifications. The proportions of CD59 erythrocytes and CD59 granulocytes from 32 healthy individuals were 0.047 ± 0.052% (range, 0–0.17%) and 0.056 ± 0.065% (range. 0–0.22%), respectively. The frequencies of AA and MDS patients with over these maximum values were 25.9% and 7.7%, respectively, in erythrocytes and 31.5% and 23.1%, respectively, in granulocytes. Thirteen (36.1%) of 36 PNH patients had lower proportions (range, 1–10%) of CD59 erythrocytes and no apparent clinical symptoms. Subsequently, the concentrations of serum Hpl in AA, MDS, and PNH patients were 127.6 ± 130.4 mg/dl (range, 7–551 mg/dl), 73.2 ± 74.3 mg/dl (range, 3–430 mg/dl), and 13.2 ± 24.6 mg/dl (range, 2–130 mg/dl), respectively. There were significant differences in the values between AA and MDS, MDS and PNH, and AA and PNH patients (p<0.01 in all comparisons). The values of serum Hpl in 436 Japanese healthy individuals were 152.4 ± 72.7 mg/dl (range, 42.6–309 mg/dl). The frequencies of AA, MDS, and PNH patients with below 40 mg/dl of serum Hpl were 27.8%, 38.5%, and 94.4%, respectively. The white blood cell counts, absolute neutrophil counts, and platelet counts in the group with low concentrations of serum Hpl in AA patients (n=15) or the concentrations of hemoglobin in that in MDS patients (n=20) significantly decreased compared with those in the group with normal concentrations of that in AA patients (n=39) or in MDS patients (n=32), respectively (p<0.005, p<0.01, and p<0.02; or p<0.05, respectively). In conclusion, our findings suggest that diagnostic criteria for PNH should be reconsidered according to proportions of GPI-negative erythrocytes, and that concentration of serum Hpl can be used as a hallmark sharply knowing existence of over 1% of GPI-negative erythrocytes in PNH.

Author notes

Disclosure: No relevant conflicts of interest to declare.