Acute Respiratory Failure Is the Initial Manifestation in the Adult-Onset A3243G tRNALeu mtDNA Mutation: A Case Report and the Literature Review

Weaning difficulty after severe pneumonia in adult-onset mitochondrial myopathy with A3243G mutation in the mitochondrial tRNA gene: A case report

Background

Mitochondrial myopathy is a group of diseases caused by abnormal mitochondrial structure or function. The mitochondrial myopathy impacts muscles of the whole body and exhibits variable symptoms. Respiratory muscle deficits deteriorate pulmonary function in patients with severe pneumonia.

Case presentation

We report the case of a male patient with severe pneumonia-induced respiratory failure. He was abnormally dependent invasive ventilator-assisted ventilation after his condition had improved. Then we found abnormal ventilator waveform and a decline in muscle strength of him. Mitochondrial myopathy was ultimately confirmed by muscle pathological biopsy and body fluid genetic testing. Vitamin B complex, coenzyme Q10, Neprinol AFD, l-arginine, and MITO-TONIC were used to improve mitochondrial function and muscle metabolism. After treatment, discomfort associated with chest tightness, fatigue, cough, and sputum disappeared, and the patient was discharged.

Conclusion

This case presented an uncommon cause of difficult weaning and extubation-acute onset of mitochondrial myopathy. Muscle biopsy and genetic testing of body fluid are essential for diagnosing mitochondrial myopathy. The A3243G mutation in the MT-TL1 gene of mitochondrial DNA contributes to pathogenesis of this case.

Mitochondrial haplotype mutation alleviates respiratory defect of MELAS by restoring taurine modification in tRNA with 3243A > G mutation

The 3243A > G in mtDNA is a representative mutation in mitochondrial diseases. Mitochondrial protein synthesis is impaired due to decoding disorder caused by severe reduction of 5-taurinomethyluridine (τm5U) modification of the mutant mt-tRNALeu(UUR) bearing 3243A > G mutation. The 3243A > G heteroplasmy in peripheral blood reportedly decreases exponentially with age. Here, we found three cases with mild respiratory symptoms despite bearing high rate of 3243A > G mutation (>90%) in blood mtDNA. These patients had the 3290T > C haplotypic mutation in addition to 3243A > G pathogenic mutation in mt-tRNALeu(UUR) gene. We generated cybrid cells of these cases to examine the effects of the 3290T > C mutation on mitochondrial function and found that 3290T > C mutation improved mitochondrial translation, formation of respiratory chain complex, and oxygen consumption rate of pathogenic cells associated with 3243A > G mutation. We measured τm5U frequency of mt-tRNALeu(UUR) with 3243A > G mutation in the cybrids by a primer extension method assisted with chemical derivatization of τm5U, showing that hypomodification of τm5U was significantly restored by the 3290T > C haplotypic mutation. We concluded that the 3290T > C is a haplotypic mutation that suppresses respiratory deficiency of mitochondrial disease by restoring hypomodified τm5U in mt-tRNALeu(UUR) with 3243A > G mutation, implying a potential therapeutic measure for mitochondrial disease associated with pathogenic mutations in mt-tRNAs.

Treatment of a patient with severe lactic acidosis and multiple organ failure due to mitochondrial myopathy: A case report

BACKGROUND

Mitochondrial myopathy is a rare genetic disease with maternal inheritance that may involve multiple organ systems. Due to the lack of typical characteristics, its clinical diagnosis is difficult, and it is often misdiagnosed or even missed.

CASE SUMMARY

The patient was a young college student. When he presented at the hospital, he had severe lactic acidosis, respiratory failure, and shock with multiple organ dysfunction syndrome (MODS). He was treated by mechanical ventilation, veno-arterial extracorporeal membrane oxygenation, and other organ support. However, his condition continued to worsen. After a thorough and detailed medical and family history was taken, a mitochondrial crisis was suspected. A muscle biopsy was taken. Further genetic testing confirmed a mitochondrial gene mutation (TRNL1 3243A>G). The final diagnosis of mitochondrial myopathy was made. Although there is no known specific treatment, intravenous methylprednisone and intravenous immunoglobulin were started. The patient's shock eventually improved. The further course was complicated by severe infection in multiple sites, severe muscle weakness, and recurrent MODS. After 2 mo of multidisciplinary management and intensive rehabilitation, the patient could walk with assistance 4 mo after admission and walk independently 6 mo after admission.

CONCLUSION

More attention should be paid to mitochondrial myopathy to avoid missed diagnosis and misdiagnosis.

Treatment of a patient with severe lactic acidosis and multiple organ failure due to mitochondrial myopathy: A case report

BACKGROUND

Mitochondrial myopathy is a rare genetic disease with maternal inheritance that may involve multiple organ systems. Due to the lack of typical characteristics, its clinical diagnosis is difficult, and it is often misdiagnosed or even missed.

CASE SUMMARY

The patient was a young college student. When he presented at the hospital, he had severe lactic acidosis, respiratory failure, and shock with multiple organ dysfunction syndrome (MODS). He was treated by mechanical ventilation, veno-arterial extracorporeal membrane oxygenation, and other organ support. However, his condition continued to worsen. After a thorough and detailed medical and family history was taken, a mitochondrial crisis was suspected. A muscle biopsy was taken. Further genetic testing confirmed a mitochondrial gene mutation (TRNL1 3243A>G). The final diagnosis of mitochondrial myopathy was made. Although there is no known specific treatment, intravenous methylprednisone and intravenous immunoglobulin were started. The patient’s shock eventually improved. The further course was complicated by severe infection in multiple sites, severe muscle weakness, and recurrent MODS. After 2 mo of multidisciplinary management and intensive rehabilitation, the patient could walk with assistance 4 mo after admission and walk independently 6 mo after admission.

CONCLUSION

More attention should be paid to mitochondrial myopathy to avoid missed diagnosis and misdiagnosis.

Treatment of a patient with severe lactic acidosis and multiple organ failure due to mitochondrial myopathy: A case report

BACKGROUND

Mitochondrial myopathy is a rare genetic disease with maternal inheritance that may involve multiple organ systems. Due to the lack of typical characteristics, its clinical diagnosis is difficult, and it is often misdiagnosed or even missed.

CASE SUMMARY

The patient was a young college student. When he presented at the hospital, he had severe lactic acidosis, respiratory failure, and shock with multiple organ dysfunction syndrome (MODS). He was treated by mechanical ventilation, veno-arterial extracorporeal membrane oxygenation, and other organ support. However, his condition continued to worsen. After a thorough and detailed medical and family history was taken, a mitochondrial crisis was suspected. A muscle biopsy was taken. Further genetic testing confirmed a mitochondrial gene mutation (TRNL1 3243A>G). The final diagnosis of mitochondrial myopathy was made. Although there is no known specific treatment, intravenous methylprednisone and intravenous immunoglobulin were started. The patient’s shock eventually improved. The further course was complicated by severe infection in multiple sites, severe muscle weakness, and recurrent MODS. After 2 mo of multidisciplinary management and intensive rehabilitation, the patient could walk with assistance 4 mo after admission and walk independently 6 mo after admission.

CONCLUSION

More attention should be paid to mitochondrial myopathy to avoid missed diagnosis and misdiagnosis.

Leigh Syndrome Spectrum: A Portuguese Population Cohort in an Evolutionary Genetic Era

Mitochondrial diseases are the most common inherited inborn error of metabolism resulting in deficient ATP generation, due to failure in homeostasis and proper bioenergetics. The most frequent mitochondrial disease manifestation in children is Leigh syndrome (LS), encompassing clinical, neuroradiological, biochemical, and molecular features. It typically affects infants but occurs anytime in life. Considering recent updates, LS clinical presentation has been stretched, and is now named LS spectrum (LSS), including classical LS and Leigh-like presentations. Apart from clinical diagnosis challenges, the molecular characterization also progressed from Sanger techniques to NGS (next-generation sequencing), encompassing analysis of nuclear (nDNA) and mitochondrial DNA (mtDNA). This upgrade resumed steps and favored diagnosis. Hereby, our paper presents molecular and clinical data on a Portuguese cohort of 40 positive cases of LSS. A total of 28 patients presented mutation in mtDNA and 12 in nDNA, with novel mutations identified in a heterogeneous group of genes. The present results contribute to the better knowledge of the molecular basis of LS and expand the clinical spectrum associated with this syndrome.

Biomarkers of mitochondrial dysfunction in acute respiratory distress syndrome: A systematic review and meta-analysis

Introduction

Acute respiratory distress syndrome (ARDS) is one of the main causes of Intensive Care Unit morbidity and mortality. Metabolic biomarkers of mitochondrial dysfunction are correlated with disease development and high mortality in many respiratory conditions, however it is not known if they can be used to assess risk of mortality in patients with ARDS.

Objectives

The aim of this systematic review was to examine the link between recorded biomarkers of mitochondrial dysfunction in ARDS and mortality.

Methods

A systematic review of CINAHL, EMBASE, MEDLINE, and Cochrane databases was performed. Studies had to include critically ill ARDS patients with reported biomarkers of mitochondrial dysfunction and mortality. Information on the levels of biomarkers reflective of energy metabolism and mitochondrial respiratory function, mitochondrial metabolites, coenzymes, and mitochondrial deoxyribonucleic acid (mtDNA) copy number was recorded. RevMan5.4 was used for meta-analysis. Biomarkers measured in the samples representative of systemic circulation were analyzed separately from the biomarkers measured in the samples representative of lung compartment. Cochrane risk of bias tool and Newcastle-Ottawa scale were used to evaluate publication bias (Prospero protocol: CRD42022288262).

Results

Twenty-five studies were included in the systematic review and nine had raw data available for follow up meta-analysis. Biomarkers of mitochondrial dysfunction included mtDNA, glutathione coupled mediators, lactate, malondialdehyde, mitochondrial genetic defects, oxidative stress associated markers. Biomarkers that were eligible for meta-analysis inclusion were: xanthine, hypoxanthine, acetone, N-pentane, isoprene and mtDNA. Levels of mitochondrial biomarkers were significantly higher in ARDS than in non-ARDS controls (P = 0.0008) in the blood-based samples, whereas in the BAL the difference did not reach statistical significance (P = 0.14). mtDNA was the most frequently measured biomarker, its levels in the blood-based samples were significantly higher in ARDS compared to non-ARDS controls (P = 0.04). Difference between mtDNA levels in ARDS non-survivors compared to ARDS survivors did not reach statistical significance (P = 0.05).

Conclusion

Increased levels of biomarkers of mitochondrial dysfunction in the blood-based samples are positively associated with ARDS. Circulating mtDNA is the most frequently measured biomarker of mitochondrial dysfunction, with significantly elevated levels in ARDS patients compared to non-ARDS controls. Its potential to predict risk of ARDS mortality requires further investigation.

Systematic review registration

[https://www.crd.york.ac.uk/prospero], identifier [CRD42022288262].

The non-syndromic clinical spectrums of mtDNA 3243A>G mutation

The m.3243A >G mutation in the tRNA Leu (UUR) gene (MT-TL1) of the mitochondrial DNA is the most widely seen pathogenic mtDNA mutation which has major phenotypic variations. The clinical phenotype involves various organs such as the brain and nerves, skeletal muscles, heart, endocrine system, gastrointestinal tract, and skin. Some phenotypes conform to well established syndromes, while most of the symptoms appear individually or concomitant to other syndromes, making identification difficult. Furthermore, some progress has been made on cardiac manifestations as well as complications during pregnancy and perinatal period. This article provides a systematic review of the non-syndromic phenotypes and latest developments in m.3243A>G mutation.

Heteroplasmy and phenotype spectrum of the mitochondrial tRNALeu (UUR) gene m.3243A>G mutation in seven Han Chinese families

The m.3243A > G mutation in the mitochondrial tRNA^{Leu (UUR)} gene is associated with a variety of phenotypic heterogeneity. The clinical spectrum and phenotypic-genotypic correlations in the Chinese patients are poorly understood. In the present study, we reported the clinical and genetic characterization, as well as haplogroups of seven Han Chinese families carrying the m.3243A > G mutation. Of the 39 matrilineal individuals, five suffered from mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), two had life-threatening mitochondrial myopathy (LTMM), and one patient had neuropathy, ataxia, and retinitis pigmentosa (NARP)-like syndrome. The LTMM and NARP like syndromes enriched the phenotypic profile of the m.3243A > G mutation. The heteroplasmy of the m.3243A > G mutation ranged from 16% to 59% in MELAS, 29% to 79% in LTMM, and 57% in a NARP-like syndrome patient. The levels ranged from 0% to 14% in patients that manifested with pure diabetes and pure hearing loss, and 0% to 5% in 13 normal family members. However, we particularly noticed heteroplasmy in four asymptomatic individuals in one LTMM family carried the heteroplasmy mutation ranged from 22% to 78%, implying that there were other modifying factors in this family. The modulation of the phenotype of mtDNA mutations requires further investigation.