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Hereditary Diseases

Question for Department of Health

UIN HL854, tabled on 7 July 2014

To ask Her Majesty’s Government, further to the Written Answer by Earl Howe on 1 April (WA 178), whether they intend to issue a clarification of the differences between the figures for the number of babies born with mitochondrial disorders in their press releases on 28 June 2013 and 27 February 2014; whether the updated disease estimate for the United Kingdom based both on data from the 2011 census and observational epidemiological studies from the north-east of England is closer to their stated figure of one in 6,500 or one in 200; what was the corresponding frequency of children in either the north-east of England or the United Kingdom as a whole that were diagnosed with each of the mitochondrial diseases listed in Annex D of the consultation document entitled "Mitochondrial Donation" over the last ten years for which data are available; and how those figures compare to available data on population frequencies for mutations within the nuclear POLG1 and POLG2 genes.

Answered on

21 July 2014

The Wellcome Centre for Mitochondrial Research at Newcastle University have estimated that there are initially 10-20 women per year, of child-bearing age, who carry faulty mitochondrial DNA (mtDNA) and who might decide that mitochondrial donation is the best reproductive option, as noted in my Written Answer of 1 April 2014.

It is estimated that at least 1 in 200 children in the United Kingdom are born with faulty mtDNA, as stated in the consultation documentation released 27 February 2014. Whereas the figure of 1 in 6,500 babies, as stated in the press release of 28 June 2013, is an estimation of those thought to go on to develop a more serious mitochondrial disorder. Serious cases can result in fatal liver failure, stroke-like episodes, blindness, muscle disease, diabetes and deafness.

Calculating the overall incidence of mitochondrial disease is extremely difficult. The figure of 1 in 200 is based on epidemiological data from the UK and Australia. This disease estimate in the UK is based on observational epidemiological studies from the north east of England which are currently being updated using the data from the 2011 census.

The table of disorders caused by unhealthy mtDNA attached as Annex D in the consultation document ‘Mitochondrial Donation’ was derived from existing published tables, such as the 2011 report by the Expert Panel convened by The Human Fertilisation and Embryology Authority to review safety and efficacy of mitochondrial donation techniques. There is currently no published information of the exact numbers of cases of each of the conditions in Annex D.