Waqar Ali, Masood Anwar.
Frequency of translocation-down syndrome in northern Pakistan.
Pak J Pathol Jan ;16(2):65-7.

Objective: To determine the proportion of Translocation-Down syndrome in patients of Down syndrome. Study design and duration: Cross sectional study carried out at Armed Forces Institute of Pathology, Rawalpindi from October 2000 to October 2002. Patients and methods: One hundred and sixty nine clinically suspected patients of Down syndrome were referred to AFIP Rawalpindi for cytogenetic confirmation during the period of study. Five ml of venous blood was collected from each case in heparinised vaccutainer tube. Blood was cultured in RPMI-1640 medium enriched with L-glutamine and foetal bovine serum. Phytohaemagglutin was used as T-cell mitogen. The cultures were incubated for 72 hours at 37°C. Mitoses were arrested in metaphase by colchicine. The cells were harvested and slides prepared and aged. These were digested with trypsin and stained with Giemsa stain. Twenty metaphases were analysed under the microscope and the observations were recorded. Results: Out of 169 patients studied, Down syndrome was confirmed in 138 (81.7%) patients on chromosomal analysis. One hundred and thirty (94.2%) of these had classical Down syndrome with 47 chromosomes (Trisomy 21). Seven (5.1%) patients had translocation variant of Down syndrome while there was one (0.7%) case of mosaic Down syndrome. The chromosomes involved in translocation were 13, 14, 15 and 21. All of these patients had the phenotype of Down syndrome. In patients with translocation variant parents were also studied. Only one mother had the same translocation as that of her child and her age was 29 years. Conclusions: Our results show that 5.1% of patients with Down syndrome phenotype have the translocation variant on cytogenetic studies. Chromosomal abnormality, however, is not commonly present in the parents. Identification of this variant is more demanding and requires thorough, meticulous examination by an experienced observer as the total number of chromosomes is 46 in contrast to 47 in the classical Down syndrome.

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