Mitochondrial respiratory chain enzyme assay and DNA analysis in peripheral blood leukocytes for the etiological study of Chinese children with Leigh syndrome due to complex I deficiency

Leigh-Like Syndrome With a Novel, Complex Phenotype Due to m.10191T>C in Mt-ND3

Leigh-like syndrome (LLS) due to the variant m.10191T>C in ND3 with a number of new phenotypic traits has not been published. In this case report, a 32-year-old woman diagnosed with Leigh-like syndrome presented with a complex novel, progressive, multisystem phenotype, manifesting in the brain (mild cognitive impairment, seizures, choreoathetosis, pseudotumor cerebri, hypersomnia, symmetric pallidal hypointensities, panda sign, calcifications, dysphagia), endocrine organs (empty sella syndrome, hypocorticism, hypoaldosteronism, hypogonadism), hematopoietic system (anemia, lymphocytosis), immune system (lymphocytosis, hypogammaglobulinemia), gut (reflux, diarrhea), kidneys (renal insufficiency, renal tubular acidosis, nephrolithiasis), muscles (myopathy, exercise intolerance, easy fatigability), peripheral nerves (small fiber neuropathy, dysautonomia), connective tissue (hyperlaxity of joints, bruising), and bones (scoliosis, Chiari malformation). A genetic workup revealed the known pathogenic variant m.10191T>C in ND3, which was also carried by the patient’s mother. This case demonstrates that the m.10191T>C variant in ND3 can phenotypically manifest with multisystem disease and that this disease is responsive to symptomatic treatment and application of additional compounds.

Development of Leigh syndrome with a high probability of cardiac manifestations in infantile-onset patients with m.14453G > A

The m.14453G > A mutation in MT-ND6 has been described in a few patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes or Leigh syndrome.However, the clinical spectrum and molecular characteristics are unclear.Here, we present four infantile-onset patients with m.14453G > A-associated Leigh syndrome. All four patients had brainstem lesions with basal ganglia lesions, and two patients had cardiac manifestations. Decreased ND6 protein expression and immunoreactivity were observed in patient-derived samples. There was no clear correlation between heteroplasmy levels and onset age or between heteroplasmy levels and phenotype; however, infantile onset was associated with Leigh syndrome.

A Chinese Family With Adult-Onset Leigh-Like Syndrome Caused by the Heteroplasmic m.10191T>C Mutation in the Mitochondrial MTND3 Gene

Leigh syndrome (LS) is a mitochondrial disease of infancy and early childhood, that is rarely seen in adults. The high degree of genetic and clinical heterogeneity makes LS a very complex syndrome. The clinical manifestations include neurological symptoms and various non-neurological symptoms, with different mutations differing in presentations and therapies. The m.10191T>C mutation in the mitochondrial DNA gene encoding in the respiratory chain complex I (CI) subunit of MTND3 results in the substitution of a highly conserved amino acid (p.Ser45Pro) within the ND3 protein, leading to CI dysfunction and causing a broad clinical spectrum of disorders that includes LS. Patients with the m.10191T>C mutation are rare in general, even more so in adults. In the present study, we report a family of patients with very rare adult-onset Leigh-like syndrome with the m.10191T>C mutation. The 24-year-old proband presented with seizures 6 years ago and developed refractory status epilepticus on admission. She had acute encephalopathy accompanied by lactic acidosis, symmetrical putamen and scattered cortical lesions. The video electroencephalogram suggested focal-onset seizures. She harbored the heteroplasmic m.10191T>C mutation in her blood and fibroblasts. Her aunt was diagnosed with mitochondrial disease at the age of 42, and had the heteroplasmic m.10191T>C mutation in her fibroblasts. Her aunt's son (cousin) died of respiratory failure at the age of 8, and we suspected he was also a case of LS. Furthermore, we reviewed the previously reported patients with the m.10191T>C mutation and summarized their characteristics. Recognizing the characteristics of these patients will help us improve the clinical understanding of LS or Leigh-like syndrome.

Clinical, biochemical, and genetic analysis of the mitochondrial respiratory chain complex I deficiency

Mitochondrial respiratory chain complex I deficiency is one of common mitochondrial disorders. However, the information is relatively little about the features of Chinese patients. In this study, the clinical, biological, and genetic analyses were performed in the children with respiratory chain complex I deficiency, in order to further understand the characteristics of the disease.Over a 3-year period, 67 patients (37 boys, 30 girls), presenting with unexplained multisystemic symptoms and signs were recruited. Clinical and laboratory data of the patients were summarized. Spectrophotometric assay was used for the analysis of mitochondrial complex I-V enzyme activity in peripheral leukocytes. The entire mitochondrial DNA (mtDNA) sequence was analysed for patients and their mothers.The children with respiratory chain complex I deficiency presented with multisystem dysfunction. Onset occurred before the third year of life in 96.9% patients without mtDNA mutation. Onset occurred before the third year of life in 76.5% of patients with mtDNA mutation (P = .03). About 51.5% of patients without mtDNA mutation had weakness, which is higher than 24% patients with mtDNA mutation (P = .02). Isolated complex I deficiency and combined complex I deficiency were found in 45 and 22 patients, respectively. The prevalence of isolated complex I deficiency was higher in the patients with mtDNA mutations (79.4%) than in the patients without mtDNA mutations (54.5%).Patients with nuclear DNA mutations are more likely to develop early onset in mitochondrial respiratory chain complex I deficiency. The patients with complex I deficiency of peripheral leukocytes may be more likely to be caused by mtDNA mutation.

Long survival in patients with leigh syndrome and the m.10191T>C mutation in MT-ND3 : a case report and review of the literature

We report an unusual case of Leigh syndrome due to the m.10191T>C mutation in the complex I gene MT-ND3. This mutation has been associated with a spectrum of clinical phenotypes ranging from infant lethality to adult onset. Despite infantile onset and severe symptoms, our patient has survived to early adulthood because of a strict dietary regimen and parental care. This patient is an extreme example of the frequently prolonged course of Leigh syndrome due to this particular mutation.

Two compound frame-shift mutations in succinate dehydrogenase gene of a Chinese boy with encephalopathy

OBJECTIVE

To investigate respiratory chain complex II deficiency resulted from mutation in succinate dehydrogenase gene (SDH) encoding complex II subunits in China.

METHODS

An 11-year-old boy was admitted to our hospital. He had a history of progressive psychomotor regression and weakness since the age of 4years. His cranial magnetic resonance imaging revealed focal, bilaterally symmetrical lesions in the basal ganglia and thalamus, indicating mitochondrial encephalopathy. The activities of mitochondrial respiratory chain enzymes I-V in peripheral leukocytes were determined via spectrophotometry. Mitochondrial DNA and the succinate dehydrogenase A (SDHA) gene were analyzed by direct sequencing.

RESULTS

Complex II activity in the leukocytes had decreased to 33.07nmol/min/mg mitochondrial protein (normal control 71.8±12.9); the activities of complexes I, III, IV and V were normal. The entire sequence of the mitochondrial DNA was normal. The SDHA gene showed two heterozygous frame-shift mutations: c.G117G/del in exon 2 and c.T220T/insT in exon 3, which resulted in stop codons at residues 56 and 81, respectively.

CONCLUSIONS

We have described the first Chinese case of mitochondrial respiratory chain complex II deficiency, which was diagnosed using enzyme assays and gene analysis. Two novel, compound, frame-shift mutations, c.G117G/del in exon 2 and c.T220T/insT in exon 3 of the SDHA gene, were found in our patient.