Retrospective observational study of the magnetic resonance imaging features of MPV17-related mitochondrial DNA depletion syndrome.

Background: MPV17-related mitochondrial deoxyribonucleic acid (DNA) maintenance defects present in most affected individuals as an early-onset encephalohepatopathic disease. Diagnosis requires comprehensive molecular genetic testing, which is often not available in resource-limited settings. Therefore, the role of imaging as a diagnostic tool necessitates further exploration. Herein, we present the largest known cohort of patients with genetically confirmed MPV17-related mitochondrial DNA depletion syndrome, highlighting in detail the neuroimaging findings.

Objective: To establish novel features on magnetic resonance imaging (MRI) that characterise MPV17-related mitochondrial DNA depletion syndrome, in order to provide a non-invasive, accessible, and reproducible biomarker inquiry.

Materials and methods: Retrospective, descriptive study based at a large tertiary level hospital. Eight patients with MPV17-related mitochondrial DNA depletion syndrome who had undergone brain MRI were identified between 2015 and 2023. Neuroimaging findings were captured and described in detail. Two board-certified radiologists with experience in paediatric neuroradiology reviewed all images by consensus.

Results: All patients were homozygous for the MPV17: c.106C>T variant. Age at brain MRI ranged from 11 days to 8 months. Seven out of the eight patients showed signal abnormalities in the reticulospinal tracts and/or reticular formation. Other neuroimaging findings included leukoencephalopathy, injury to extra-reticular white matter tracts and frequent basal ganglia involvement. Newly identified areas of involvement include the perirolandic cortices, hippocampi, optic pathways and olfactory nerves.

Conclusion: Lesions in the reticular formation and reticulospinal tracts on brain MRI in a neonate or infant with hepatic dysfunction may represent a distinctive, albeit not specific, feature of MPV17-related mitochondrial DNA depletion syndrome.