A case-comparison study of pregnant women with mitochondrial disease - what to expect?

OBJECTIVE

Mitochondrial disease is a disorder of energy metabolism that affects 1 in 4300 adults in the UK. Pregnancy is associated with physiological demands that have implications for energy metabolism. We were interested to know how pregnancy was affected in women with mitochondrial disease, particularly those with the most common pathogenic mutation m.3243A>G.

DESIGN

Retrospective case-comparison study.

POPULATION/SETTING

Sixty-seven women with genetically confirmed mitochondrial disease from the UK Mitochondrial Diseases Cohort and 69 unaffected women participated.

METHODS

Participants answered questionnaires regarding each of their pregnancies. Patients were divided into two groups according to genetic mutation, with those harbouring m.3243A>G comprising a single group.

MAIN OUTCOME MEASURES

Pregnancy-related complications, mode of delivery, gestational age and birthweight of newborns.

RESULTS

Of 139 live births in the comparison group, 62 were in the m.3243A>G group and 87 were in the 'all other mutations' group. Pregnancies of women with the m.3243A>G mutation had significantly more gestational diabetes (odds ratio [OR] = 8.2, 95% CI 1.3-50.1), breathing difficulties (OR = 7.8, 95% CI 1.0-59.1) and hypertension (OR = 8.2, 95% CI 3.1-21.5) than the comparison group. Only half of the pregnancies in the m.3243A>G group had normal vaginal delivery, with emergency caesarean section accounting for 24.2% of deliveries. Babies were born significantly earlier to mothers harbouring m.3243A>G with 53.3% of them preterm (<37 weeks). These babies were also more likely to require resuscitation and admission.

CONCLUSION

Women who carried the m.3243A>G mutation appeared to be at higher risk of complications during pregnancies, caesarean section and preterm delivery than the unaffected women or those with other forms of mitochondrial disease.

TWEETABLE ABSTRACT

Pregnant women with mitochondrial disease - m.3243A>G mutation - are at greatly increased risk of complications and preterm delivery.

Natural disease course and genotype-phenotype correlations in Complex I deficiency caused by nuclear gene defects: what we learned from 130 cases

Mitochondrial complex I is the largest multi-protein enzyme complex of the oxidative phosphorylation system. Seven subunits of this complex are encoded by the mitochondrial and the remainder by the nuclear genome. We review the natural disease course and signs and symptoms of 130 patients (four new cases and 126 from literature) with mutations in nuclear genes encoding structural complex I proteins or those involved in its assembly. Complex I deficiency caused by a nuclear gene defect is usually a non-dysmorphic syndrome, characterized by severe multi-system organ involvement and a poor prognosis. Age at presentation may vary, but is generally within the first year of life. The most prevalent symptoms include hypotonia, nystagmus, respiratory abnormalities, pyramidal signs, dystonia, psychomotor retardation or regression, failure to thrive, and feeding problems. Characteristic symptoms include brainstem involvement, optic atrophy and Leigh syndrome on MRI, either or not in combination with internal organ involvement and lactic acidemia. Virtually all children ultimately develop Leigh syndrome or leukoencephalopathy. Twenty-five percent of the patients died before the age of six months, more than half before the age of two and 75 % before the age of ten years. Some patients showed recovery of certain skills or are still alive in their thirties . No clinical, biochemical, or genetic parameters indicating longer survival were found. No clear genotype-phenotype correlations were observed, however defects in some genes seem to be associated with a better or poorer prognosis, cardiomyopathy, Leigh syndrome or brainstem lesions.