RESUMEN
To determine the frequency of cytogenetic abnormalities in patients diagnosed as primary myelodysplastic syndrome [MDS] using conventional karyotyping. Case series. The Clinical Laboratory. The Aga Khan University Hospital, Karachi, between January 2006 - June 2012. Patients of all ages and either gender who fulfilled WHO criteria for MDS were included. Cytogenetic analysis was conducted at the time of diagnosis. Patients who had secondary MDS were excluded from analysis. Chromosome identification and karyotype description was done according to the International System for Chromosome Nomenclature [ISCN, 1995] and described as frequency percentage. Out of the 122 cases of MDS, 71 patients had their karyotype done at the time of diagnosis, including 42 males [59.2%] and 29 females [40.8%] with median age of 60 years. Forty one [57.7%] showed normal karyotype and 30 [42.3%] showed clonal karyotypic abnormalities at diagnosis. Out of which 14 [19.7%] had single, 11 [15.5%] had complex and 6 [8.5%] had double cytogenetic abnormalities. The common abnormalities found were: trisomy 8 in 7 cases [9.9%], -7/del [7q] in 3 cases [4.2%], -Y and complex 5q in 2 cases [2.8%] each, complex trisomy 8, del 11q, inversion 9, trisomy 19 and del 20q were found in 1 case [1.4%] each. Other abnormalities were found in 11 cases [15.5%]. Trisomy 8 was the most common disorder/abnormality found in this study population followed by the complex cytogenetics