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LBSL: Case Series and DARS2 Variant Analysis in Early Severe Forms With Unexpected Presentations
Menno D Stellingwerff1, Sonia Figuccia1, Emanuele Bellacchio1
1Department of Child Neurology, Emma Childrens Hospital, Amsterdam University Medical Centers, Vrije Universiteit and Amsterdam Neuroscience, The Netherlands (M.D.S., T.E.M.A.); Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Italy (S.F., C.D., P.G.); Area di Ricerca Genetica e Malattie Rare (E.B.), Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy; Laboratory of Oncology and Molecular Genetics (K.A.), Clínica las Condes, Santiago, Chile; Department of Pediatric Neurology (C.C.), Clínica Las Condes, Santiago, Chile; Division of Child Neurology (P.T.), Department of Neurology, Istanbul Faculty of Medicine, Turkey; Department of Paediatrics (C.A.S.), Royal Childrens Hospital, Murdoch Childrens Research Institute and University of Melbourne, Victoria, Australia; Pediatric Neurology (C.E.E.), Radboud University Medical Center, Amalia Childrens Hospital, Nijmegen, The Netherlands; Department of Pediatrics (A.S.-V.), University of South Florida, Tampa; Unit of Pediatric Neurology and Neurorehabilitation (S.L.), Department WomanMother-Child, Lausanne University Hospital, Switzerland; Community Pediatrics, Royal Berkshire Hospital, Reading (S.H.), United Kingdom; Neuropediatric Department (T.S.-M.), Childrens Hospital, Luzern, Switzerland; Unit of Neurorehabilitation (G.V.), Department of Neurosciences, Bambino Gesù Children's Research Hospital, IRCCS, Rome, Italy; Paediatric Neurology (G.C.), Nottingham Childrens Hospital, United Kingdom; PEDEGO Research Unit (E.R.), Medical Research Center and Department of Clinical Genetics, University of Oulu and Oulu University Hospital, Finland; Radiology (C.O.), Clínica las Condes, Santiago, Chile; Unit of Neuromuscular and Neurodegenerative Disorders (E.S.B), Area di Ricerca Genetica e Malattie Rare and Department of Neurosciences, Bambino Gesù Children's Research Hospital, IRCCS, Rome, Italy; and Department of Child Neurology (M.S.v.d.K.), Emma Childrens Hospital and Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, the Netherlands.
Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) shows diverse MRI phenotypes due to DARS2 variants. These findings expand LBSL diagnosis and reveal severe neuronal involvement in affected patients.
Area of Science:
- Neurogenetics
- Mitochondrial Biology
- Neuroimaging
Background:
- Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a leukodystrophy linked to DARS2 gene variants.
- Classic LBSL presents with specific MRI long tract abnormalities and is typically mild.
- Unusual MRI findings prompted investigation into novel LBSL phenotypes.
Purpose of the Study:
- To investigate unusual MRI presentations in 15 patients diagnosed with LBSL.
- To determine if these cases represent consistent novel LBSL phenotypes.
- To analyze the impact of DARS2 variants on mitochondrial aspartyl-tRNA synthetase (mtAspRS) function.
Main Methods:
- Review of clinical data, MRI findings, and genetic variants in 15 patients.
- Whole Exome Sequencing (WES) for variant identification.
- Functional studies assessing mtAspRS structure and mitochondrial function.
Main Results:
- Two distinct MRI phenotypes were identified: severe cerebral hypoplasia/atrophy (Group 1) and white matter abnormalities without long tract involvement (Group 2).
- Group 1 exhibited more severe phenotypes, including antenatal onset and microcephaly.
- DARS2 variants were more severe in these cases compared to classic LBSL, with missense variants affecting critical mtAspRS functional regions.
Conclusions:
- DARS2 variants cause highly heterogeneous LBSL phenotypes, including profound cerebral hypoplasia/atrophy and white matter abnormalities.
- These findings broaden the diagnostic spectrum of LBSL.
- Severe cases suggest dominant neuronal/axonal involvement, supported by mouse model data.
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