Journal
JOURNAL OF MEDICAL GENETICS
Volume 54, Issue 2, Pages 114-124Publisher
BMJ PUBLISHING GROUP
DOI: 10.1136/jmedgenet-2016-103876
Keywords
mDNA mutations; de novo; prenatal diagnosis (PND); genetic counselling
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Funding
- Wellcome Trust Centre for Mitochondrial Research [096919Z/11/Z]
- Medical Research Council (UK) Centre for Translational Muscle Disease Research [G0601943]
- Lily Foundation
- UK NHS Highly Specialised Commissioners
- 'Rare Mitochondrial Disorders of Adults and Children' Diagnostic Service in Newcastle upon Tyne
- National Institute for Health Research (NIHR) doctoral fellowship [NIHRHCS-D12-03-04]
- MRC [G0601943] Funding Source: UKRI
- National Institute for Health Research [NIHR-HCS-D12-03-04] Funding Source: researchfish
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Background Severe, disease-causing germline mitochondrial (mt)DNA mutations are maternally inherited or arise de novo. Strategies to prevent transmission are generally available, but depend on recurrence risks, ranging from high/unpredictable for many familial mtDNA point mutations to very low for sporadic, large-scale single mtDNA deletions. Comprehensive data are lacking for de novo mtDNA point mutations, often leading to misconceptions and incorrect counselling regarding recurrence risk and reproductive options. We aim to study the relevance and recurrence risk of apparently de novo mtDNA point mutations. Methods Systematic study of prenatal diagnosis (PND) and recurrence of mtDNA point mutations in families with de novo cases, including new and published data. De novo' based on the absence of the mutation in multiple (postmitotic) maternal tissues is preferred, but mutations absent in maternal blood only were also included. Results In our series of 105 index patients (33 children and 72 adults) with (likely) pathogenic mtDNA point mutations, the de novo frequency was 24.6%, the majority being paediatric. PND was performed in subsequent pregnancies of mothers of four de novo cases. A fifth mother opted for preimplantation genetic diagnosis because of a coexisting Mendelian genetic disorder. The mtDNA mutation was absent in all four prenatal samples and all 11 oocytes/embryos tested. A literature survey revealed 137 de novo cases, but PND was only performed for 9 (including 1 unpublished) mothers. In one, recurrence occurred in two subsequent pregnancies, presumably due to germline mosaicism. Conclusions De novo mtDNA point mutations are a common cause of mtDNA disease. Recurrence risk is low. This is relevant for genetic counselling, particularly for reproductive options. PND can be offered for reassurance.
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