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Feb 06, 2013, 09.05 PM IST | Source: PTI

Now, diagnosis of some genetic birth disorders to be easier

Diagnosis of some genetic birth disorders will now be easier thanks to a next-generation tool devised by genetic scientists.

Diagnosis of some genetic birth disorders will now be easier thanks to a next-generation tool devised by genetic scientists.

A family in Ahmedabad had three unexplained infant deaths in sequence, aged 3, 5 and 8 months and all had suffered from the symptoms before succumbing to hyperthermia (excessive body temperature) sometime in 2010.

But their cause was eventually traced by the Sir Ganga Ram Hospital here as a genetic defect before parents and other doctors failed to diagnose the unexplained rise in temperature in the infants' bodies. And the tool used was a next-generation diagnosis technique called the "exome sequencing" which has proved quite useful for many patients since the death of the three children earlier.

The Ahmedabad family is a case study as part of the genetic research on this new diagnosis tool, done in collaboration with experts from India and abroad and has been published in the 'Journal of Medical Genetics' titled "Genetic Diagnosis of Unexplained Infant's Death by Exome Sequencing" a few days back, a study member said.

"Exome sequencing is proving as a useful tool for diagnosing hitherto undiagnosed genetic disorders like the children in the Ahmedabad case and have benefited many since then here," Sunita Bijrania, consultant in Genetic Medicine at the Sir Ganga Ram Hospital here and a co-author in the study, told PTI.

"We had received blood samples of the last child (8-month-old) sometime in December and we had extracted the DNA too but the child couldn't survive. This was the first case of diagnosis using exome sequencing but, after him 4-5 patients' genetic disorders have been diagnosed through this new tool after existing methods failed," she said.

She explained this new technique works by "sequencing only the part of the gene involved in protein-making and thus reducing the size of sampling many fold and the incurred cost".

Exome sequencing would mean in layman terms "selectively sequencing the coding region of the genome, as in like an all-in-one tool instead of going through all the 22,000 genes that we have".

"Human exome consists of 1 per cent of the entire genome so it is possible to get more out of little reads. Also it is quicker, easier and means less effort for the doctors,"
Bijrania said.

She said that the "cost of one treatment would be like USD 10,000 and in terms of genes, ranges from Rs 24,000 to a lakh or two per gene".

"We had another case that came up at the hospital from Punjab wherein four generations suffered from the same symptom of Alzheimer's by age 30 and all died before reaching 40. They wee also diagnosed through exome sequencing only before their deaths could not be explained," Bijarnia said.

In medical terms, an exome is the part of the genome formed by exons, and constitute the collection of all the coding regions. The exome of the human genome consists of roughly 180,000 exons constituting about 1 per cent of the total genome.

Earlier in the day, Congress President Sonia Gandhi launched in Maharashtra a new initiative of universal child health screening for birth defects and deficiencies that can lead to disabilities, as well as early intervention services that will cover an estimated 27 crore children.

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