Relationship Between Myelodysplastic Syndrome and Paroxysmal Nocturnal Hemoglobinuria: Spanish Erythropathology Group and Spanish Paroxysmal Nocturnal Hemoglobinuria Working Group Experience

INTRODUCTION

PNH clones appear frequently in patients with myelodysplastic syndrome (MDS) and aplastic anemia (AA) which may even evolve into classic PNH. It has been described isolated cases of clonal evolution from AA, through classic PNH and MDS; and at the end, acute leukemia (AL) has rarely been described. These patients show a progressive replacement of the PNH clone by a dysplastic one carrying a monosomy of chromosome 7.

OBJECTIVE

We designed a retrospective study of patients included in the database of the Spanish PNH Registry in search of patients with a MDS and a PNH clone or those with a classic PNH who evolved into MDS. Our aim was to study the characteristics of patients who showed some of these entities and AA history.

RESULTS

Our search retrieved 6 patients, of whom 3 were MDS cases with a small PNH clone (Table 1). One of the patients had had a previous classic PNH followed by a MDS. The remaining two patients had been diagnosed with AA, developing classical PNH and MDS later; of these, one (patient 2) died with an acute leukemia.

The median follow-up time was 83 (range 56-480) months, while the follow-up time from diagnosis of MDS was 68 (range 6-108) months. The patient characteristics are describe in Table 1.

There are two remarkable features, diagnosis of a RAEB-1 in two cases and the frequency of trisomies of chromosome 8 and 21 and deletion of chromosome 7. These chromosomal abnormalities appeared sequentially as MDS evolved in 3 patients. The PNH clone disappeared in those patients who developed a MDS after an AA/classic PNH and persisted in those MDS cases who showed a PNH clone at diagnosis of MDS.

CONCLUSIONS

Patients with a diagnosis of AA, classic PNH or MDS with a PNH clone must be followed up for life, with bone marrow studies with karyotype and measurements of the PNH clone, to rule out the development of other hematological entities. Our series is a small one and only studies with a larger number of patients will allow us to establish definitive conclusions. The inclusion of these patients in the International PNH Registry is strongly advised.