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.