A mutation in mt tRNALeu(UUR) causing a neuropsychiatric syndrome with depression and cataract

A Multisystem Mitochondrial Disease Caused by a Novel MT-TL1 mtDNA Variant: A Case Report

BACKGROUND

Mitochondrial tRNA (MTT) genes are hotspot for mitochondrial DNA mutation and are responsible of half mitochondrial disease. MTT mutations are associated with a broad spectrum of phenotype often with complex multisystem involvement and complex genotype-phenotype correlations. MT-TL1 mutations, among which the m.3243A>G mutation is the most frequent, are associated with myopathy, maternal inherited diabetes and deafness, MELAS, cardiomyopathy, and focal segmental glomerulosclerosis.

CASE STUDY

Here we report the case of an Italian 49-years old female presenting with encephalomyopathy, chronic proteinuric kidney disease and a new heteroplasmic m.3274_3275delAC MT-TL1 gene mutation.

CONCLUSIONS

Our case demonstrates a systemic mitochondrial disease caused by the heteroplasmic m.3274_3275delAC MT-TL1 gene mutation, not yet described in the literature. A mitochondrial disease should be suspected in case of complex multisystem phenotypes, including steroid-resistant nephrotic syndrome with multisystemic involvement.

Cognitive characteristics of mitochondrial diseases in children

INTRODUCTION

This retrospective descriptive study was undertaken to further define the intelligence profiles of children with mitochondrial disorders, in the context of seizures and age of symptom onset.

METHODS

We retrospectively identified forty-nine pediatric patients with definitive mitochondrial disease diagnoses and complete intelligence or adaptive functioning testing data. Patients were 0-216 months at onset of symptoms and 61-250 months of age at testing. Twenty-four of 49 patients had seizures. Twenty-one of the 24 patients with seizures had medically intractable seizures. All patients had Wechsler Intellectual Quotient (IQ) testing, except nine patients with seizures who were unable to engage in IQ testing and were assessed with a structured parent interview measure, the Vineland Adaptive Behavior Scales. We used descriptive and exploratory data analysis methods to characterize test results.

RESULTS

Distribution of ages for patients with the Vineland assessment was younger than those given the Wechsler. The median overall score (combining Wechsler and Vineland summary scores) for all patients was 85 (interquartile range [IQR]: 50, 102), with the group without seizures obtaining a higher median Full Scale IQ (FSIQ) of 100 (IQR: 86, 109), compared to the group with seizures with a median FSIQ of 67 (IQR: 49.5, 89), a difference that is both statistically and clinically different (Δ = 33; 95% CI: 9, 52). The adaptive function measure was composed of patients only with intractable epilepsy and yielded the lowest overall median summary score of 43 (IQR: 37, 50). This general trend in differences between the FSIQ scores of the groups with and without seizures was also seen across all subscale measures analyzed-IQ index scores and two subtest scores, Digit Span and Coding-though differences were not always statistically different. Vargha-Delaney's A effect sizes ranged between 0.68 and 0.90, trends that mirrored those of distributional and median differences. Groups without versus with seizures differed most distinctly in Performance IQ (PIQ), with the group without seizures' median PIQ being 100 (IQR 94, 112) versus the group with seizures' median PIQ being 63 (IQR 54, 84), a difference of 37 points (95% CI).

DISCUSSION

Results suggest that patients with mitochondrial diseases with seizures and early onset disease represent a worse cognitive phenotype, as compared with those with no seizures, who can have average intelligence. Results are discussed in the context of current literature.

Adult-onset of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome with hypothyroidism and psychiatric disorders

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a clinical syndrome associated with mitochondrial disorders (MIDs). This report illustrates a case of MELAS syndrome with hypothyroidism and psychiatric disorders, which is different from the common clinical manifestations of MELAS syndrome, such as exercise intolerance, migraine-like headaches, hearing loss and seizures etc. There are considerable interests in the possibility that mitochondrial dysfunction may play a role in the pathogenesis of endocrine dysfunctions and psychiatric disorders in MELAS syndrome.

Mood and anxiety disorders as early manifestations of medical illness: a systematic review

BACKGROUND

Affective disturbances involving alterations of mood, anxiety and irritability may be early symptoms of medical illnesses. The aim of this paper was to provide a systematic review of the literature with qualitative data synthesis.

METHODS

MEDLINE, PsycINFO, EMBASE, Cochrane, and ISI Web of Science were systematically searched from inception to February 2014. Search terms were 'prodrome/early symptom', combined using the Boolean 'AND' operator with 'anxiety/depression/mania/hypomania/irritability/irritable mood/hostility', combined with the Boolean 'AND' operator with 'medical illness/medical disorder'. PRISMA guidelines were followed.

RESULTS

A total of 21 studies met the inclusion criteria and were analyzed. Depression was found to be the most common affective prodrome of medical disorders and was consistently reported in Cushing's syndrome, hypothyroidism, hyperparathyroidism, pancreatic and lung cancer, myocardial infarction, Wilson's disease, and AIDS. Mania, anxiety and irritability were less frequent.

CONCLUSIONS

Physicians may not pursue medical workup of cases that appear to be psychiatric in nature. They should be alerted that disturbances in mood, anxiety and irritability may antedate the appearance of a medical disorder.

Cognitive dysfunction in mitochondrial disorders

Among the various central nervous system (CNS) manifestations of mitochondrial disorders (MIDs), cognitive impairment is increasingly recognized and diagnosed (mitochondrial cognitive dysfunction). Aim of the review was to summarize recent findings concerning the aetiology, pathogenesis, diagnosis and treatment of cognitive decline in MIDs. Among syndromic MIDs due to mitochondrial DNA (mtDNA) mutations, cognitive impairment occurs in patients with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome, myoclonus epilepsy with ragged-red fibres syndrome, mitochondrial chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, neuropathy, ataxia and retinitis pigmentosa syndrome and maternally inherited diabetes and deafness. Among syndromic MIDs due to nuclear DNA (nDNA) mutations, cognitive decline has been reported in myo-neuro-gastro-intestinal encephalopathy, mitochondrial recessive ataxia syndrome, spinocerebellar ataxia with encephalopathy, Mohr-Tranebjaerg syndrome, leuko-encephalopathy; brain and spinal cord involvement and lactic acidosis, CMT2, Wolfram syndrome, Wolf-Hirschhorn syndrome and Leigh syndrome. In addition to syndromic MIDs, a large number of non-syndromic MIDs due to mtDNA as well as nDNA mutations have been reported, which present with cognitive impairment as the sole or one among several other CNS manifestations of a MID. Delineation of mitochondrial cognitive impairment from other types of cognitive impairment is essential to guide the optimal management of these patients. Treatment of mitochondrial cognitive impairment is largely limited to symptomatic and supportive measures. Cognitive impairment may be a CNS manifestation of syndromic as well as non-syndromic MIDs. Correct diagnosis of mitochondrial cognitive impairment is a prerequisite for the optimal management of these patients.

Mitochondrial DNA (mtDNA) and schizophrenia

The poorly understood aetiology of schizophrenia is known to involve a major genetic contribution even though the genetic factors remain elusive. Most genetic studies are based on Mendelian rules and focus on the nuclear genome, but current studies indicate that other genetic mechanisms are probably involved. This review focuses on mitochondrial DNA (mtDNA), a maternally inherited, 16.6-Kb molecule crucial for energy production that is implicated in numerous human traits and disorders. The aim of this review is to summarise the studies that have explored mtDNA in schizophrenia patients and those which provide evidence for its implication in this illness. Alterations in mitochondrial morphometry, brain energy metabolism, and enzymatic activity in the mitochondrial respiratory chain suggest a mitochondrial dysfunction in schizophrenia that could be related to the genetic characteristics of mtDNA. Moreover, evidence of maternal inheritance and the presence of schizophrenia symptoms in patients suffering from a mitochondrial disorder related to an mtDNA mutation suggest that mtDNA is involved in schizophrenia. The association of specific variants has been reported at the molecular level; however, additional studies are needed to determine whether the mitochondrial genome is involved in schizophrenia.

Prevalence of Epilepsy among Cataract Patients

PURPOSE

To evaluate the prevalence of epilepsy among patients undergoing cataract surgery.

DESIGN

A retrospective observational case control study.

METHODS

We calculated the prevalence of epilepsy among all the patients older than 50 years who underwent cataract surgery (years 2000-2007, n = 12,984) in a district of the largest health maintenance organization in Israel (the Central District of Clalit Health Services) and among 25,968 age and gender matched controls. The database was screened for epilepsy by integrating the clinical and ancillary work-up as well as the drug regimen. The use of anti-epileptic drugs (AEDs) was evaluated among the cataract patients and the controls. The main outcome measure was the prevalence of epilepsy and antiepileptic medical treatment among patients undergoing cataract surgery versus controls.

RESULTS

No difference was found in demographics among the groups including age, gender, marriage status, socioeconomic class and living place between the study and control groups (except for patients origin). Epilepsy was found to be significantly more prevalent in patients undergoing cataract surgery. The odds ratio (OR) was 1.3 (95% confidence interval (CI): 1.1-1.6): 1.4 in men (95% CI: 1.1-1.9) and 1.2 in women (95% CI: 1.0-1.6). AEDs, particularly clonazepam (OR = 1.5, 95% CI: 1.1-2.1) and carbamazepine (OR = 1.4, 95% CI: 1.05-1.8), were also used more by cataract patients. Multivariate logistic regression analysis revealed a significant association between cataract surgery and epilepsy (OR 1.26, p < 0.001) as well as diabetes (OR 1.38, p < 0.001), arterial hypertension (OR 1.26, p < 0.001), smoking (OR 1.22, p < 0.001), hyperlipidemia (OR 1.12, p < 0.001), and Ashkenazi origin (OR 0.85, p < 0.001).

CONCLUSIONS

Epilepsy is associated with the presence of cataract. Various hypotheses may explain this finding, including a cataractogenic role of AEDs.

Different effects of novel mtDNA G3242A and G3244A base changes adjacent to a common A3243G mutation in patients with mitochondrial disorders

Two novel mitochondrial DNA base changes were identified at both sides of the 3243A>G mutation, the most common mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). One was a 3244G>A transition in a girl with MELAS. The other was a 3242G>A transition in a girl with a mitochondrial disorder without a MELAS phenotype. Although the two base changes were adjacent to the 3243A>G mutation, they had different effects on the clinical phenotype, muscle pathology, and respiratory chain enzyme activity. Investigations of the different effects of the 3244G>A and 3242G>A base changes may provide a better understanding of tRNA dysfunction in mitochondrial disorders.

Human mitochondrial transfer RNAs: role of pathogenic mutation in disease

The human mitochondrial genome encodes 13 proteins. All are subunits of the respiratory chain complexes involved in energy metabolism. These proteins are translated by a set of 22 mitochondrial transfer RNAs (tRNAs) that are required for codon reading. Human mitochondrial tRNA genes are hotspots for pathogenic mutations and have attracted interest over the last two decades with the rapid discovery of point mutations associated with a vast array of neuromuscular disorders and diverse clinical phenotypes. In this review, we use a scoring system to determine the pathogenicity of the mutations and summarize the current knowledge of structure-function relationships of these mutant tRNAs. We also provide readers with an overview of a large variety of mechanisms by which mutations may affect the mitochondrial translation machinery and cause disease.

Resting muscle pain as the first clinical symptom in children carrying the MTTK A8344G mutation

The characteristic clinical presentation, especially the appearance of muscle symptoms, is quite unique in children carrying the mtA8344G mutation. The diagnosis of MERRF syndrome is seldom made in the pediatric age. Fatigue is a common finding in children of pubertal age. Fatigue in combination with recurrent resting muscle pain occurs frequently in the initial phase of various hereditary muscle disorders and in several autoimmune, endocrine and metabolic syndromes. In the absence of obvious biochemical/metabolic abnormalities and in the lack of neurological symptoms the complaints are frequently labelled as fibromyalgia or chronic fatigue syndrome. In patients with behavioural or psychiatric abnormalities one might even start to question the organic etiology of the complaints. We describe a family carrying the classic MTTK mutation with a variable degree of heteroplasmy, presenting in childhood as isolated recurrent muscle pain as the first symptom of the disease.

Psychiatric comorbidity in 36 adults with mitochondrial cytopathies

INTRODUCTION

Mitochondria are intracellular organelles involved in adenosine triphosphate production. The literature has established the presence of mitochondrial dysfunction in some subjects with psychiatric disorders. Also, there are multiple reports of patients with mitochondrial dysfunction who have various psychiatric disorders. Although the literature on mitochondrial dysfunction and its relation to psychiatric disorders is growing, there remain many unanswered questions.

OBJECTIVE

To review subjects with mitochondrial cytopathies for prevalence of psychiatric comorbidity.

METHODS

For this study, 36 adults were interviewed. The Mini International Neuropsychiatric Interview and the Short-Form 36 Health Survey, version 1 were used.

RESULTS

Lifetime diagnoses included 54% major depressive disorder, 17% bipolar disorder, and 11% panic disorder. These prevalence rates are compared with the general population and subjects with cancer and epilepsy. Subjects with a comorbid psychiatric diagnosis were older (P=.05), had more hospital admissions (P=.02), more medical conditions (P=.01), and lower quality of life (P=.01) than subjects with mitochondrial disease alone.

CONCLUSION

Clinicians caring for persons with mitochondrial cytopathies should note the high prevalence of psychiatric problems. Also, this comorbidity might have etiological and therapeutic implications.

Central nervous system manifestations of mitochondrial disorders

The central nervous system (CNS) is, after the peripheral nervous system, the second most frequently affected organ in mitochondrial disorders (MCDs). CNS involvement in MCDs is clinically heterogeneous, manifesting as epilepsy, stroke-like episodes, migraine, ataxia, spasticity, extrapyramidal abnormalities, bulbar dysfunction, psychiatric abnormalities, neuropsychological deficits, or hypophysial abnormalities. CNS involvement is found in syndromic and non-syndromic MCDs. Syndromic MCDs with CNS involvement include mitochondrial encephalomyopathy, lactacidosis, stroke-like episodes syndrome, myoclonic epilepsy and ragged red fibers syndrome, mitochondrial neuro-gastrointestinal encephalomyopathy syndrome, neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome, mitochondrial depletion syndrome, Kearns-Sayre syndrome, and Leigh syndrome, Leber's hereditary optic neuropathy, Friedreich's ataxia, and multiple systemic lipomatosis. As CNS involvement is often subclinical, the CNS including the spinal cord should be investigated even in the absence of overt clinical CNS manifestations. CNS investigations comprise the history, clinical neurological examination, neuropsychological tests, electroencephalogram, cerebral computed tomography scan, and magnetic resonance imaging. A spinal tap is indicated if there is episodic or permanent impaired consciousness or in case of cognitive decline. More sophisticated methods are required if the CNS is solely affected. Treatment of CNS manifestations in MCDs is symptomatic and focused on epilepsy, headache, lactacidosis, impaired consciousness, confusion, spasticity, extrapyramidal abnormalities, or depression. Valproate, carbamazepine, corticosteroids, acetyl salicylic acid, local and volatile anesthetics should be applied with caution. Avoiding certain drugs is often more beneficial than application of established, apparently indicated drugs.

Review of the literature on major mental disorders in adult patients with mitochondrial diseases

Mitochondria are intracellular organelles crucial to the production cellular energy. Mitochondrial disease results from a malfunction in this biochemical cascade. These disorders can affect any organ system, producing diverse signs and symptoms, including psychiatric ones. Several authors argue that mitochondrial dysfunction is related to the pathophysiology of bipolar disorder and schizophrenia. Also, the authors retrieved 19 case reports that describe patients with mitochondrial diseases and psychiatric disorders. Most of these patients have psychiatric presentations that preceded the diagnosis of mitochondrial disease. The most common physical findings are fatigue, muscle weakness with or without atrophy, and hearing loss.

Comprehensive expression analysis of a rat depression model

Herein we report on a large-scale analysis of gene expression in the 'learned helplessness' (LH) rat model of human depression, using DNA microarrays. We compared gene expression in the frontal cortex (FC) and hippocampus (HPC) of untreated controls, and LH rats treated with saline (LH-S), imipramine or fluoxetine. A total of 34 and 48 transcripts were differentially expressed in the FC and HPC, respectively, between control and LH-S groups. Unexpectedly, only genes for NADH dehydrogenase and zinc transporter were altered in both the FC and HPC, suggesting limited overlap in the molecular processes from specific areas of the brain. Principal component analysis revealed that sets of upregulated metabolic enzyme genes in the FC and downregulated genes for signal transduction in the HPC can distinguish clearly between depressed and control animals, as well as explain the responsiveness to antidepressants. This comprehensive data could help to unravel the complex genetic predispositions involved in human depression.

A novel mitochondrial tRNA(Leu(UUR)) mutation in a patient with features of MERRF and Kearns-Sayre syndrome

In a patient with clinical features of both myoclonus epilepsy ragged-red fibers (MERRF) and Kearns-Sayre syndrome (KSS), we identified a novel guanine-to-adenine mitochondrial DNA (mtDNA) mutation at nucleotide 3255 (G3255A) of the tRNA(Leu(UUR)) gene. Approximately 5% of the skeletal muscle fibers had excessive mitochondria by succinate dehydrogenase histochemistry while a smaller proportion showed cytochrome c oxidase (COX) deficiency. In skeletal muscle, activities of mitochondrial respiratory chain complexes I, I + III, II + III, and IV were reduced. The G3255A transition was heteroplasmic in all tissues tested: muscle (53%), urine sediment (67%), peripheral leukocytes (22%), and cultured skin fibroblasts (< 2%). The mutation was absent in 50 control DNA samples. Single-fiber analysis revealed a higher proportion of mutation in COX-deficient RRF (94% +/- 5, n = 25) compared to COX-positive non-RRF (18% +/- 9, n = 21). The identification of yet another tRNA(Leu(UUR)) mutation reinforces the concept that this gene is a hot-spot for pathogenic mtDNA mutations.