Molecular Genetics and Metabolism Reports 26 (2021) 100690 Contents lists available at ScienceDirect Molecular Genetics and Metabolism Reports journal homepage: www.elsevier.com/locate/ymgmr Short Communication Leigh syndrome associated with TRMU gene mutations Júlia Sala-Coromina a, Lucía Dougherty-de Miguel a, Javier de las Heras b, Amaia Lasa-Aranzasti c, Elena Garcia-Arumi c, d, e, Lidia Carreño d, e, Jose Antonio Arranz f, Clara Carnicer f, María Unceta-Suárez g, Angel Sanchez-Montañez h, Laura Gort e, i, Frederic Tort e, i, Mireia del Toro a, e, * a Pediatric Neurology Department, Vall d’Hebron University Hospital, Universitat Autónoma de Barcelona, Spain b Division of Pediatric Metabolism, Cruces University Hospital, Biocruces-Bizkaia Health Research Institute, CIBER-ER; University of the Basque Country (UPV/EHU), Spain c Department of Clinical and Molecular Genetics, Vall d’Hebron University Hospital, Universitat Autónoma de Barcelona, Spain d Research Group on Neuromuscular and Mitochondrial Disorders, Vall d’Hebron Institut de Recerca (VHIR), Vall d’Hebron Hospital Universitari, Barcelona, Spain e Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain f Metabolic Laboratory, Vall d’Hebron University Hospital, Universitat Autónoma de Barcelona, Spain g Biochemistry Laboratory (Metabolism Area), Cruces University Hospital, Biocruces-Bizkaia Health Research Institute, CIBER-ER, University of the Basque Country (UPV/EHU), Spain h Pediatric Neuroradiology Department, Vall d’Hebron University Hospital, Universitat Autónoma de Barcelona, Spain i Inborn Errors of Metabolism, Biochemistry and Molecular Genetics Department, Hospital Clínic, IDIBAPS, Faculty of Medicine and Health Science-University of Barcelona, Internal Medicine Service-Hospital Clínic of Barcelona, Spain A R T I C L E I N F O A B S T R A C T Keywords: tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) deficiency causes an early onset poten­ TRMU tially reversible acute liver failure, so far reported in less than 30 patients. We describe two new unrelated Acute liver failure patients with an acute liver failure and a neuroimaging compatible with Leigh syndrome (LS) due to TRMU Leigh syndrome deficiency, a combination not previously reported. Our report enlarges the phenotypical spectrum of TRMU Mitochondrial disease disease. 1. Introduction We present two recently diagnosed patients with acute liver failure caused by TRMU pathogenic variants associated to LS, a phenotypic TRMU is a nuclear gene that encodes the mitochondrial-specific combination not previously reported. tRNA-modifying enzyme: 5-methylaminomethyl-2-thiouridylate meth­ yltransferase. TRMU pathogenic variants were first reported as a mod­ 2. Case reports ifier in patients with sensorineural deafness carrying homoplasmic m.1555G > A variant in the mitochondrial gene MTRNR1 (OMIM We extensively searched the literature for patients with TRMU *561000) [1]. In 2009, pathogenic variants in TRMU gene were molecularly confirmed disease and clinical description. Supplementary described as responsible for acute liver failure in the first months of age Table 1 summarizes clinical, laboratory, radiological and genetic data (OMIM #613070) [2]. Patients who survived this life-threatening period described in TRMU patients in previously published patients (n = 26) fully recovered and had a normal development without recurrence. To and we added our two patients (Patient 1 is P27, Patient 2 is P28). our knowledge, 26 patients with TRMU pathogenic variants have been Patient 1, a girl, was the second child of non-consanguineous par­ published. Since the first description of reversible hepatic failure, only a ents. She was born at term after an uneventful pregnancy. Her psycho­ few other phenotypes with extra-hepatic manifestations have been re­ motor development and growth parameters (weight, length and head ported. Leigh syndrome (LS), featured by hyperlactacidemia and sym­ circumference at +0.2 SD) were normal until the age of 3 months, when metrical lesions in brainstem, basal ganglia and other brain structures, is she presented a rapid deterioration and failure to thrive. She suffered the most common pediatric presentation of mitochondrial disease [3]. progressive generalized hypotonia, fluctuating level of consciousness, * Corresponding author at: Pediatric Neurology Department, Vall d’Hebron University Hospital, Passeig de la Vall d’Hebron, 119-129, Barcelona 08035, Spain. E-mail address: mdeltoro@vhebron.net (M. del Toro). https://doi.org/10.1016/j.ymgmr.2020.100690 Received 15 September 2020; Received in revised form 19 November 2020; Accepted 24 November 2020 2214-4269/© 2020 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). J. Sala-Coromina et al. Molecular Genetics and Metabolism Reports 26 (2021) 100690 decreased intake, weight-loss (− 2 SD) and progressive hepatomegaly. transaminases and coagulopathy. Brain MRI showed T2 hyperintense Laboratory findings showed acute liver failure, metabolic acidosis and supra and infratentorial lesions affecting bilateral thalami, subthalamic persistent high lactate in blood, urine and CSF. Brain MRI showed acute nuclei and brainstem and a lactate peak on MRS (See Fig. 1E-O). Further and symmetrical lesions of pontinus tracts, upper cerebellar peduncles, metabolic investigations showed high lactate/pyruvate ratio, important basal nuclei and white matter, with restriction on DWI and a lactate peak elevation of intermediate metabolites of Krebs cycle in urine, and on MRS (See Fig. 1A-D). Abdominal ultrasound showed an increased size hyperalaninemia. Under the suspicion of a mitochondrial disorder, and echogenicity of the liver, without any other pathological findings. treatment with coenzyme Q, riboflavin, thiamine and biotin were Echocardiography, EEG and ophthalmologic examinations were normal. initiated with no clinical improvement. He showed a refractory hyper­ The respiratory chain complex activities in muscle biopsy were lactacidaemia (15–20 mmol/L) and died at the age of 25 days from a decreased except for normal CII, and increased citrate synthase activity. multiple organ failure. The respiratory chain complexes activities were Muscle biopsy findings suggested mitochondrial myopathy (see suppl measured in muscle and, except for CII, all of them and also citrate table). Lactic acidosis correction and supplementation with carnitine, synthase activity were decreased. When analyzing their ratio, most of biotine and thiamine was initiated with transient clinical and them became normalized, so no significant alterations were detected. biochemical improvement. After two months the patient was readmitted The low activity of all complexes and also of citrate synthase, could to PICU with severe hepatic failure, coagulopathy, tubulopathy and indicate a low number of mitochondria in the muscle. Mitochondrial lactic acidosis, refractory to all treatments and she died at the age of 6 DNA sequencing was normal. Exome Sequencing showed two patho­ months. genic variants in TRMU: c.2 T > A: p.Met1? (reported in [2]) and Mitochondrial DNA sequencing was normal. Clinical whole exome c.491delT: p.Leu164ProfsTer22 (non-previously reported, but also sequencing (TruSight One®, Illumina, San Diego) demonstrated two pathogenic according to ACMG rules due to frameshift change gener­ mutations in trans in TRMU gene: c.160_161delTG:p.Cys54* (non-pre­ ating premature stop codon). Most relevant findings in patient’s nec­ viously reported, but likely pathogenic according to ACMG criteria since ropsy were: massive hepatic steatosis, increase in heart thickness at the it creates an stop codon) and c.680G > C:p.Arg227Thr (previously expense of groups of vacuolated and granular cytoplasm myocytes, described in [4]). Parents were carriers of these variants. among which conserved myocytes were identified, and severe spongi­ Patient 2, a boy, was the first child of non-consanguineous parents. otic vacuolization in thalamus, midbrain, trunk and focal cerebellum. After a non-complicated pregnancy, he was born at term with low birth- In summary, both patients presented an early onset Leigh syndrome weight (− 2.7 SD). During the first 12 h of life he presented generalized and an acute liver failure with progression to multiorganic failure and hypotonia with severe lactic acidosis, progressive elevation of fatal outcome due to TRMU variants, and can not be explained by other Fig. 1. MRI of patient 1 (P27 in the supplementary table) showed symmetrical lesions of pontinus tracts, upper cerebellar peduncles, basal nuclei and white matter with restriction in DWI (A-D). MRI of patient 2 (P28 in the suppl table) showed an increased lactate peak in the MRS (E), supra and infratentorial lesions affecting bilateral thalami, subthalamic nuclei and brainstem in DWI (F-J) and T2 (K-O). 2 J. Sala-Coromina et al. Molecular Genetics and Metabolism Reports 26 (2021) 100690 genetic findings in the whole exome-sequencing. caused by mtDNA pathogenic variants. Both isolated and multiple complex deficiencies can be found, being these last ones mainly caused 3. Discussion by mutations in more than 150 proteins implicated in mitochondrial translation, including TRMU [15]. Axial and/or peripheral hypotonia We report two recently diagnosed unrelated patients with TRMU was described in four patients (P15, P16, P18 and P19), P25 had seizure- pathogenic variants, associating LS and acute liver failure, a combina­ like episodes and mild developmental delay has been reported in P24 tion not previously reported. and P26. Although neurological involvement has been described in some Classical presentation of TRMU pathogenic variants has been patients, none of them had brain lesions compatible with Leigh described to date in 26 patients with acute liver failure as the main syndrome. phenotype, some of which share other clinical findings (Supplementary TRMU encodes a protein that participates in the modification of table) [2,5–12]. Almost all (24/26) reported patients suffered from he­ mitochondrial tRNAs. Specifically, it is responsible for the 2-thiolation patic failure. One (P18) had a myopathic phenotype (ptosis, fatigability, of the nucleotide at the wobble position of the tRNA-Lys, tRNA-Glu, bulbar involvement with feeding and respiratory difficulties at onset and t-RNA-Gln [2]. Many other genes related to mitochondrial trans­ with complete recovery) and another (P20) a fatal heart failure in his lation are identified to cause Leigh syndrome [13,14]. Similar patho­ first month of life. Other extrahepatic manifestations include a variable genic mechanisms could be shared between these genes to explain Leigh range of symptoms: reversible dilated cardiomyopathy and neph­ syndrome in our patients, but further investigations are needed to un­ romegaly (P4), bulbar involvement with feeding difficulties (P18,P19), derstand why only a few patients with TRMU pathogenic variants some degree of hypotonia (P15, P17, P18), hypothyroidism, macrocytic developed this phenotype. anemia and microcephaly (P21, P22), ichthyosis (P24), etc. Long-term Although most of the reported patients (19/26) experienced a partial outcome varies from complete recovery (19/26) to death due to liver, or total recovery after the acute phase, all of our patients died during the heart or multiorganic failure (7/26). When surviving the acute phase, first months of life. They presented severe neurological involvement and most patients have a normal development and complete recovery. finally died from multiorganic failure. However, long term follow-up data are not available for all of these A possible explanation to clarify a genotype-phenotype correlation patients. Regarding biochemical findings, all patients showed increased has been proposed [2]: patients carrying two missense variants (except serum lactate level (3.2–40.0 mmol/L), with variable range of lactate in those occurring in first methionine) seem to have better prognosis than CSF (from normal, to 3.9 mmol/L). Abnormal liver function was present when, nonsense, frameshift or splicing variants are present. Both pa­ in all patients (available data from 24/26) with variable degrees of tients carried nonsense and frameshift variants respectively, in com­ transaminase elevation, coagulopathy, cholestasis or elevated alfa- pound heterozygosity with known missense pathogenic variants. On the fetoprotein. Liver biopsies (9/23) showed signs of mild to severe he­ other hand, first descriptions of TRMU defects suggested increasing patic involvement in biopsies taken several months after onset: onco­ cysteine availability in later infancy as a possible explanation for clinical cytic changes in the hepatocytes, focal steatosis and focal ballooning of recovery [2]. Patient 2 had an abnormal birth weight, which may induce cytoplasm, micronodular cirrhosis, canalicular cholestasis to patent thinking that cysteine deficiency in maternal and neonatal nutrition signs of fibrosis, irregular cirrhosis with nodulation and macrovesicular could also be a potential contributor to a severe phenotype. However, steatosis. No normal hepatic biopsies were reported. Analysis of respi­ patient 1 had normal weight before clinical deterioration at 3 months ratory chain enzyme activities demonstrated a combined respiratory old. Therefore, we conclude that neither molecular findings nor chain complex deficiency in most of the cases with available data (11/ maternal/neonatal nutrition seem reason enough to explain the clinical 26). Brain MRI was performed in 17/26 patients. All except three were heterogeneity of the disorder. normal. P16 had a lactate peak in MRI with no lesions, P15 had myeli­ To conclude, TRMU gene sequencing should be considered in pa­ nation delay with normal MRS and P19 had a reversible T2 high signal in tients with Leigh syndrome, especially when liver involvement is pre­ right thalamus with lactate peak in MRS. sent, and also in patients with other mitochondrial phenotypes as Our patients are similar to the ones reported in literature in terms of progressive failure to thrive, mild-moderate psychomotor delay, mild liver failure and abnormal laboratory findings. In contrast, our patients liver involvement and metabolic acidosis with hyperlactacidemia. presented a neurological clinical onset consisted of an acute encepha­ Further patient reports and more investigations are needed to explain lopathy and developmental regression (P1) and severe hypotonia from this phenotypical variability even though carrying same pathogenic birth (P2). All two displayed symmetrical and bilateral lesions in MRI variants. Our report enlarges the phenotypical spectrum of TRMU affecting different brain structures consistent with LS, with a lactate disease. peak on MRS. Postmortem study in P2 demonstrated massive hepatic steatosis, also seen in liver biopsies of previous patients and spongiotic Funding vacuolization in thalamus, midbrain, trunk and focal cerebellum as seen in LS [3]. Interestingly, this necropsy showed cardiac affection, despite This work was partially supported by the Spanish Instituto de Salud the patient not having presented evident cardiological symptoms. Only Carlos III, Fondo de Investigaciones Sanitarias and cofounded with two previous patients (P4, P20) were mentioned to have cardiological ERDF funds (Grant No. FIS PI15/01428, PI19/01772). involvement. Clinical presentation of Leigh syndrome varies depending on the age Author statement of onset [13]. In typical infantile onset, initial nonspecific manifesta­ tions can be seen: vomiting, hypotonia, failure to thrive or develop­ All persons who meet authorship criteria are listed as authors, and all mental delay, often with acute worsening of previous clinical state after authors certify that they have participated sufficiently in the work to a clinical event such as infection. On the other hand, liver involvement it take public responsibility for the content, including participation in the is a very unusual clinical manifestation. Bilateral symmetrical lesions concept, design, analysis, writing, or revision of the manuscript. within the brainstem, basal ganglia and less frequent white matter, T2- Furthermore, each author certifies that this material or similar material W in MRI characterize the disease with elevated lactate in MRS [14]. has not been and will not be submitted to or published in any other Both clinical and neuroimaging features occurred in our two patients. publication before this submission. Pathogenic variants in over 75 genes (nuclear and mitochondrial DNA), have been associated to Leigh syndrome [14], despite what, half of the Authorship contributions cases remain without a genetic diagnosis [13]. Defects of nuclear DNA genes are the main cause of Leigh syndrome, with only 25% of all cases Specific author contributions are listed below. 3 J. Sala-Coromina et al. Molecular Genetics and Metabolism Reports 26 (2021) 100690 • Júlia Sala-Coromina: Conceptualization, methodology, visualization, O. Elpeleg, Acute infantile liver failure due to mutations in the TRMU gene, Am. J. Hum. Genet. 85 (2009) 401–407, https://doi.org/10.1016/j.ajhg.2009.08.004. writing – original draft. [3] N.J. Lake, M.J. Bird, P. Isohanni, A. Paetau, Leigh syndrome: neuropathology and • Lucía Dougherty-de Miguel: Conceptualization, methodology, visu­ pathogenesis, J. Neuropathol. Exp. Neurol. 74 (2015) 482–492, https://doi.org/ alization, writing – original draft. 10.1097/NEN.0000000000000195. • Javier de las Heras: Conceptualization, methodology, writing. [4] L. Meng, M. Pammi, A. Saronwala, P. Magoulas, A.R. Ghazi, F. Vetrini, J. Zhang, W. He, A.V. Dharmadhikari, C. Qu, P. Ward, A. Braxton, S. Narayanan, X. Ge, M. • Amaia Lasa-Aranzasti: Methodology, data curation and review. J. Tokita, T. Santiago-Sim, H. Dai, T. Chiang, H. Smith, M.S. Azamian, L. Robak, B. • Elena Garcia-Arumi: Methodology, supervision, writing review. L. Bostwick, C.P. Schaaf, L. Potocki, F. Scaglia, C.A. Bacino, N.A. Hanchard, M. • Lidia Carreño: Methodology, data curation F. Wangler, D. Scott, C. Brown, J. Hu, J.W. Belmont, L.C. Burrage, B.H. Graham, V. R. Sutton, W.J. Craigen, S.E. Plon, J.R. Lupski, A.L. Beaudet, R.A. Gibbs, D. • Jose Antonio Arranz:.Methodology, data curation. M. Muzny, M.J. Miller, X. Wang, M.S. Leduc, R. Xiao, P. Liu, C. Shaw, • Clara Carnicer: Methodology, data curation. M. Walkiewicz, W. Bi, F. Xia, B. Lee, C.M. Eng, Y. Yang, S.R. Lalani, Use of exome • María Unceta-Suárez: Methodology, data curation. sequencing for infants in intensive care units ascertainment of severe single-gene disorders and effect on medical management, JAMA Pediatr. 171 (2017) 1–11, • Angel Sanchez-Montañez: Methodology, writing review. and editing. https://doi.org/10.1001/jamapediatrics.2017.3438. • Laura Gort: Methodology, data curation, writing review. [5] U. Schara, J.C. Von Kleist-Retzow, E. Lainka, P. Gerner, A. Pyle, P.M. Smith, • Frederic Tort: Methodology, writing review. H. Lochmüller, B. Czermin, A. Abicht, E. Holinski-Feder, R. Horvath, Acute liver failure with subsequent cirrhosis as the primary manifestation of TRMU mutations, • Mireia del Toro: Conceptualization, methodology, supervision, J. Inherit. Metab. Dis. 34 (2011) 197–201, https://doi.org/10.1007/s10545-010- writing review and editing. 9250-z. [6] P. Gaignard, E. Gonzales, O. Ackermann, P. Labrune, I. Correia, P. Therond, E. Jacquemin, A. 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