[DNM1L gene variant caused encephalopathy, lethal, due to defective mitochondrial peroxisomal fission 1: three cases report and literature review]

Abstract

Objective: To investigate the clinical characteristics of R403C variant in DNM1L gene caused encephalopathy, lethal, due to defective mitochondrial peroxisomal fission 1 (EMPF1). Methods: The clinical data of three patients, who carried R403C variant in the DNM1L gene, diagnosed at Xiangya Hospital from February 2018 to February 2020 were retrospectively summarized. Literature reviewing was performed by taking "DNM1L" or "encephalopathy, lethal, due to defective mitochondrial peroxisomal fission 1" as keywords for searching in online Mendelian inheritance in man (OMIM), PubMed, China national knowledge infrastructure (CNKI), and Wanfang data knowledge service platform up to July 2020. And the clinical manifestation, laboratory examination, imaging, treatment, and prognosis were reviewed. Results: Case 1, a 7-year-old boy, developed seizures after a 9-day course of cough without fever. The seizures manifested as generalized tonic-clonic seizures (GTCS) and soon converted to focal status epilepticus (EPC) or focal myoclonus, which were resistant to multi-anti-epileptic drugs combined with sedative drugs. The boy died at the 2^nd week after seizure onset. Case 2, also a 7-year-old boy, developed seizures after a 10-day history of amygdalitis. The seizures manifested as focal to generalized tonic-clonic seizure and then converted to EPC or focal myoclonus. And all seizures showed poor responses to multi-anti-epileptic drugs combined with sedative drugs, ketogenic diet, and methylprednisolone treatment. The boy died after 1 month's treatment. Case 3, a 3-year and 5-month old girl, had seizures onset after a 2-week course of viral pneumonia. The seizures onset manifested as focal clonic seizure and converted to EPC, shortly. She was resistant to multi-anti-epiletic drugs combined with sedative drugs and ketogenic treatment. The girl died 3 months afte seizure onset. All of their images showed multifocal T1 low, T2, fluid attenuated inversion recovery, and diffusion-weighted imaging high signal lesions among the brain, and diffuse brain atrophy in case 3. The blood metabolic and cerebrospinal-fluid immunological assays were normal. Genetic analysis suggested a de novo, heterozygous, NM_012062.4: c.1207C>T, p.R403C variant in the DNM1L gene. According to their clinical manifestations, all of them were diagnosed with EMPF1. Literature review included 11 patients carrying this variant in the world. Summarizing the 14 cases, 8 cases had an infectious history before seizure onset, 8 cases had mild or moderate development delay. All of 14 cases had seizures, and the forms mainly included EPC (n=9), focal myoclonus (n=6), GTCS (n=5) and focal clonic seizures (n=4). All of them were refractory, and no effective anti-epileptic drugs were recommended. Early-stage cranial magnetic resonance imaging results showed multiple intracranial focal lesions (n=10), including thalamus (n=7), hippocampus (n=5), basal ganglia (n=4), frontal lobe (n=3), and temporal lobe (n=2). As the disease progressed, the brain manifested as diffused progressive atrophy (n=10). Five of the 14 cases died at reported age. Conclusions: R403C variant in the DNM1L gene can cause mitochondrial fission dysfunction. Patients carrying this variant may manifest as refractory status epilepticus with or without mild-infection indction, development regression and brain atrophy.