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Published on: June 15, 2018
Early and lethal neurodegeneration with myasthenic and myopathic features: A new ALG14-CDG
David C Schorling1, Simone Rost1, Dirk J Lefeber1
1From the Division of Neuropaediatrics and Muscle Disorders (D.C.S., R.K., M. Beytia, J.K.) and Center of Pediatric and Adolescent Medicine (M.K.), Faculty of Medicine, Medical Center, University of Freiburg; Department of Human Genetics (S.R., C.R.M., M. Beytia), Biozentrum, University of Würzburg, Germany; Department of Neurology, Translational Metabolic Laboratory, Donders Institute for Brain, Cognition and Behavior (D.J.L.), and Radboud Center for Mitochondrial Medicine, Department of Pediatrics (R.J.R.), Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatrics (Neuromuscular and Neurometabolic Disorders) (L.B., M.T.), McMaster Children's Hospital, Hamilton, Canada; Neuromuscular and Neurogenetic Disorders of Childhood Section (C.G.B.), National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD; Departments of Child Neurology (M. Bugiani, M.v.d.K.) and Pathology (M. Bugiani), VU University Medical Center; and Department of Functional Genomics (M.v.d.K.), VU University, Amsterdam Neuroscience, Amsterdam, the Netherlands.
Objective:
To describe the presentation and identify the cause of a new clinical phenotype, characterized by early severe neurodegeneration with myopathic and myasthenic features.
Methods:
This case study of 5 patients from 3 families includes clinical phenotype, serial MRI, electrophysiologic testing, muscle biopsy, and full autopsy. Genetic workup included whole exome sequencing and segregation analysis of the likely causal mutation.
Results:
All 5 patients showed severe muscular hypotonia, progressive cerebral atrophy, and therapy-refractory epilepsy. Three patients had congenital contractures. All patients died during their first year of life. In 2 of our patients, electrophysiologic testing showed abnormal decrement, but treatment with pyridostigmine led only to temporary improvement. Causative mutations in ALG14 were identified in all patients. The mutation c.220 G>A (p.Asp74Asn) was homozygous in 2 patients and heterozygous in the other 3 patients. Additional heterozygous mutations were c.422T>G (p.Val141Gly) and c.326G>A (p.Arg109Gln). In all cases, parents were found to be heterozygous carriers. None of the identified variants has been described previously.
Conclusions:
We report a genetic syndrome combining myasthenic features and severe neurodegeneration with therapy-refractory epilepsy. The underlying cause is a glycosylation defect due to mutations in ALG14. These cases broaden the phenotypic spectrum associated with ALG14 congenital disorders of glycosylation as previously only isolated myasthenia has been described.
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