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P.123 Severe DNM1 Encephalopathy with Dysmyelination due to Recurrent Splice Site Pathogenic Variant

Published online by Cambridge University Press:  05 January 2022

AN Sahly
Affiliation:
(Montreal)*
E Krochmalnek
Affiliation:
(Montreal)
J St-Onge
Affiliation:
(Montreal)
M Srour
Affiliation:
(Montreal)
KA Myers
Affiliation:
(Montreal)
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Abstract

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Background: Patients with DNM1-encephalopathy almost exclusively have missense variants, mostly in the GTPase domain of DNM1. Delayed myelination has been reported in at least three patients with DNM1-encephalopathy, all with missense mutations in the DNM1 central domain. Only one DNM1 splice-site variant has previously been reported, and the authors questioned whether the variant accounted for all aspects of the patient’s phenotype. Methods: Case-Report. Results: Our patient had hypotonia and brief multifocal tonic seizures from age-1-month. He still has profound global developmental delay, daily seizures and microcephaly. MRI-Brain at age-21-months showed T2 hyperintensity in the bilateral periventricular and subcortical white matter; spectroscopy showed a questionable lactate peak and an elevated choline peak relative to N-acetylaspartate. Clinical gene-panel identified a heterozygous de novo pathogenic variant in intron 9 of DNM1 (c.1197-8G > A; IVS9- 8G>A). In-silico tools categorized this variant as deleterious secondary to a splicing defect. RT-PCR analysis on peripheral blood was unsuccessful as DNM1 expression is extremely low outside of the brain. Conclusions: Our patient carried the same DNM1 variant previously reported, indicating this is a recurrent pathogenic splice-site variant. The spectroscopic abnormalities suggest a possible element of demyelination in DNM1 variants of the central domain, though the mechanism remains unclear.

Type
Poster Presentations
Copyright
© The Author(s), 2021. Published by Cambridge University Press on behalf of Canadian Neurological Sciences Federation