Risk of developing a mitochondrial DNA deletion disorder

Area of Science:

• Genetics
• Mitochondrial Biology
• Human Disease

Background:

• Pathogenic mitochondrial DNA (mtDNA) mutations affect at least 1 in 8000 individuals.
• Currently, no effective treatments exist for mtDNA disorders, emphasizing the importance of disease prevention.
• Many patients have a single pathogenic mtDNA deletion, but risk factors for new cases and recurrence are unknown.

Purpose of the Study:

• To investigate the relationship between maternal age and the risk of unaffected mothers having children with mtDNA deletion disorders.
• To determine recurrence risks of mtDNA deletion disorders among siblings and offspring of affected individuals.

Main Methods:

• A multicenter study involving 226 families with a proband identified with a single mtDNA deletion.
• Included patients with chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, or Pearson's syndrome.
• Analyzed the association between maternal age and the risk of affected offspring, and calculated recurrence risks.

Main Results:

• No correlation was found between maternal age and the risk of unaffected mothers having children with mtDNA deletion disorders.
• None of the 251 siblings of index cases developed clinical features of mtDNA disease.
• The risk of recurrence among offspring of affected women was 4.11% (approximately 1 in 24 births).

Conclusions:

• The incidence of mtDNA deletion disorders is not influenced by maternal age, unlike nuclear chromosomal rearrangements.
• Unaffected mothers are unlikely to have more than one child with an mtDNA deletion disorder.
• The risk of affected women having clinically affected offspring is approximately 1 in 24, a higher risk than previously assumed.