Therapy may unmask hypoplastic myelodysplastic syndrome that mimics aplastic anemia

BACKGROUND. Rarely, patients who present with pancytopenia and are diagnosed initially with aplastic anemia (AA) subsequently develop a myelodysplastic syndrome (MDS). There has been controversy regarding whether the initial diagnosis of AA is correct or whether these patients have hypocellular MDS at the onset of pancytopenia. METHODS. The authors studied bone marrow (BM) specimens from patients who were diagnosed initially with AA and subsequently with MDS from a cohort of 128 consecutive patients who had AA during the period from 1993 to 2004. Cytogenetic and fluorescence in situ hybridization (FISH) analyses were performed to assess for monosomy 7 retrospectively in a subset of patients. RESULTS. Twelve patients were identified (age range, 26-79 years). At the time they were diagnosed with AA, there was no evidence of dysplasia, the median BM cellularity was 5% (range, from <1% to 15%), and all patients had a normal karyotype. Therapy for 11 patients included immunomodulating agents, which were accompanied by growth factors in 4 patients and 1 patient underwent BM transplantation. One patient received growth factors only. The median interval to the diagnosis of MDS was 9 months (range, 2-43 months). The median BM cellularity was 30% (range, 5-90%), and dysplastic changes were observed in all patients. Nine patients had an abnormal karyotype, and monosomy 7 was the most common abnormality (n = 5 patients). FISH detected monosomy 7 in 6 samples at the time MDS was diagnosed and in 2 samples at the time AA was diagnosed. CONCLUSIONS. The detection of monosomy 7 in specimens that were considered AA and the short time interval to a subsequent diagnosis of MDS suggests that these patients had hypoplastic MDS at the onset of pancytopenia. Therapy may allow the detection of MDS by enhancing cell growth.