Distribution of hand function by age in individuals with Rett syndrome

Objective

To determine the longitudinal distribution of hand function skills in individuals with classic Rett Syndrome (RTT), an X-linked dominant neurodevelopmental disorder, and correlate with MECP2 variants.

Method

We conducted a longitudinal study of 946 girls and young women with typical RTT seen between 2006 and 2021 in the US Natural History Study (NHS) featuring a structured clinical evaluation to assess the level of hand function skills. The specific focus in this study was to assess longitudinal variation of hand skills from age 2 through age 18 years in relation to specific MECP2 variant groups.

Results

Following the initial regression period, hand function continues to decline across the age spectrum in individuals with RTT. Specific differences are noted with steeper declines in hand function among those with milder variants (Group A: R133C, R294X, R306C, and C-terminal truncations) compared to groups composed of individuals with more severe variants.

Conclusions

These temporal variations in hand use represent specific considerations which could influence the design of clinical trials that test therapies aiming to ameliorate specific functional limitations in individuals with RTT. Furthermore, the distinct impact of specific MECP2 variants on clinical severity, especially related to hand use, should be considered in such interventional trials.

Anxiety-like behavior and anxiolytic treatment in the Rett syndrome natural history study

BACKGROUND

Rett syndrome (RTT) is a neurodevelopmental disorder most often related to a pathogenic variant in the X-linked MECP2 gene. Internalizing behaviors appear to be common, but standard methods of diagnosing anxiety are not readily applied in this population which typically has cognitive impairment and limited expressive language. This study aims to describe the frequency of anxiety-like behavior and anxiolytic treatments along with associated clinical features in individuals with RTT.

METHODS

Parental reports and medication logs provided data from 1380 females with RTT participating in two iterations of the multicenter U.S. RTT Natural History Study (RNHS) from 2006 to 2019.

RESULTS

Most participants with RTT (77.5%) had at least occasional anxious or nervous behavior. Anxiety was reported to be the most troublesome concern for 2.6%, and within the top 3 concerns for 10.0%, of participants in the second iteration. Parents directly reported treatment for anxious or nervous behavior in 16.6% of participants in the second iteration with most reporting good control of the behavior (71.6%). In the medication logs of both RNHS iterations, the indication of anxiety was listed for a similar number of participants (15% and 14.5%, respectively). Increased use of anxiolytics and selective serotonin reuptake inhibitors (SSRIs) was related to more frequent anxiety-like behaviors (P < 0.001), older age (P < 0.001), and mild MECP2 variants (P = 0.002).

CONCLUSION

Anxiety-like behavior is frequent at all ages and is a significant parental concern in RTT. Older individuals and those with mild MECP2 variants are more likely to be treated with medications. Better diagnosis and treatment of anxiety in RTT should be a goal of both future studies and clinical care.

TRIAL REGISTRATION

NCT00299312 and NCT02738281.

Levetiracetam Versus Phenobarbital for Neonatal Seizures: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

There are no US Food and Drug Administration-approved therapies for neonatal seizures. Phenobarbital and phenytoin frequently fail to control seizures. There are concerns about the safety of seizure medications in the developing brain. Levetiracetam has proven efficacy and an excellent safety profile in older patients; therefore, there is great interest in its use in neonates. However, randomized studies have not been performed. Our objectives were to study the efficacy and safety of levetiracetam compared with phenobarbital as a first-line treatment of neonatal seizures.

METHODS

The study was a multicenter, randomized, blinded, controlled, phase IIb trial investigating the efficacy and safety of levetiracetam compared with phenobarbital as a first-line treatment for neonatal seizures of any cause. The primary outcome measure was complete seizure freedom for 24 hours, assessed by independent review of the EEGs by 2 neurophysiologists.

RESULTS

Eighty percent of patients (24 of 30) randomly assigned to phenobarbital remained seizure free for 24 hours, compared with 28% of patients (15 of 53) randomly assigned to levetiracetam (P < .001; relative risk 0.35 [95% confidence interval: 0.22-0.56]; modified intention-to-treat population). A 7.5% improvement in efficacy was achieved with a dose escalation of levetiracetam from 40 to 60 mg/kg. More adverse effects were seen in subjects randomly assigned to phenobarbital (not statistically significant).

CONCLUSIONS

In this phase IIb study, phenobarbital was more effective than levetiracetam for the treatment of neonatal seizures. Higher rates of adverse effects were seen with phenobarbital treatment. Higher-dose studies of levetiracetam are warranted, and definitive studies with long-term outcome measures are needed.

Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes

Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis‐characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.

Endocrine Disorders in Primary Mitochondrial Disease

Context

Endocrine disorders are common in individuals with mitochondrial disease. To develop evidence-based screening practices in this high-risk population, updated age-stratified estimates of the prevalence of endocrine conditions are needed.

Objective

To measure the point prevalence of selected endocrine disorders in individuals with mitochondrial disease.

Design, Setting, and Patients

The North American Mitochondrial Disease Consortium Patient Registry is a large, prospective, physician-curated cohort study of individuals with mitochondrial disease. Participants (n = 404) are of any age, with a diagnosis of primary mitochondrial disease confirmed by molecular genetic testing.

Main Outcome Measures

Age-specific prevalence of diabetes mellitus (DM), abnormal growth and sexual maturation (AGSM), hypoparathyroidism, and hypothyroidism.

Results

The majority of our sample was pediatric (<18 years; 60.1%), female (56.9%), and white (85.9%). DM affected 2% of participants aged <18 years [95% confidence interval (CI): 0.4% to 5.7%] and 24.4% of adult participants (95% CI: 18.6% to 30.9%). DM prevalence was highest in individuals with mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes syndrome (MELAS; 31.9%, of whom 86.2% had the m.3243A>G mutation). DM occurred more often with mitochondrial DNA defects (point mutations and/or deletions) than with nuclear DNA mutations (23.3% vs 3.7%, respectively; P < 0.001). Other prevalence estimates were 44.1% (95% CI: 38.8% to 49.6%) for AGSM; 0.3% (95% CI: 0% to 1.6%) for hypoparathyroidism; and 6.3% (95% CI: 4% to 9.3%) for hypothyroidism.

Conclusion

DM and AGSM are highly prevalent in primary mitochondrial disease. Certain clinical mitochondrial syndromes (MELAS and Kearns-Sayre/Pearson syndrome spectrum disorders) demonstrated a higher burden of endocrinopathies. Clinical screening practices should reflect the substantial prevalence of endocrine disorders in mitochondrial disease.

Microwave ablation of focal hepatic malignancies regardless of size: A 9-year retrospective study of 64 patients

PURPOSE

To retrospectively evaluate the safety and efficacy of microwave ablation (MWA) as treatment for single, focal hepatic malignancies.

MATERIALS AND METHODS

Institutional review board approval was obtained for this HIPAA-compliant study. From December 2003 to May 2012, 64 patients were treated with MWA for a single hepatic lesion, in 64 sessions. Hepatocellular carcinoma (HCC) was treated in 25 patients (geometric mean tumor size, 3.33-cm; 95% CI, 2.65-4.18-cm; range, 1.0-12.0-cm), metastatic colorectal cancer (CRC) was treated in 27 patients (geometric mean tumor size, 2.7-cm; 95% CI, 2.20-3.40-cm; range, 0.8-6.0-cm), and other histological-types were treated in 12 patients (geometric mean tumor size, 3.79-cm; 95% CI, 2.72-5.26-cm; range, 1.7-8.0-cm). Kaplan-Meier (K-M) method was used to analyze time event data. Chi-square and correlation evaluated the relationship between tumor size and treatment parameters.

RESULTS

Technical success rate was 95.3% (61/64). Treatment parameters were tailored to tumor size; as size increased more antennae were used (p<0.001), treatment with multiple activations increased (p<0.028), and treatment time increased (p<0.001). There was no statistically significant relationship between time to recurrence and tumor size, number of activations, number of antennae, and treatment time. At one-year, K-M analysis predicted a likelihood of local recurrence of 39.8% in HCC patients, 45.7% in CRC metastases patients, and 70.8% in patients with other metastases. Median cancer specific survivals for patients were 38.3 months for HCC patients, 36.3 months for CRC metastases, and 13.9 months for other histological-types. Complications occurred in 23.4% (15/64) of sessions.

CONCLUSION

In our sample, tumor size did not appear to impact complete ablation rates or local recurrence rates for focal hepatic malignancies treated with MWA.

Platelet mitochondrial activity and pesticide exposure in early Parkinson's disease

BACKGROUND

Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD), but the cause of this dysfunction is unclear.

METHODS

Platelet mitochondrial complex I and I/III (nicotinamide adenine dinucleotide cytochrome c reductase, NCCR) activities were measured in early PD patients and matched controls enrolled in a population-based case-control study. Ambient agricultural pesticide exposures were assessed with a geographic information system and California Pesticide Use Registry.

RESULTS

In contrast to some previous reports, we found no differences in complex I and I/III activities in subjects with PD and controls. We did find that NCCR activity correlated with subjects' exposure to pesticides known to inhibit mitochondrial activity regardless of their diagnosis.

CONCLUSIONS

Electron transport chain (ETC) activity is not altered in PD in this well-characterized cohort when compared with community-matched controls but appears to be affected by environmental toxins, such as mitochondria-inhibiting pesticides.

Assessing bioenergetic compromise in autism spectrum disorder with 31P magnetic resonance spectroscopy: preliminary report

We sought to examine, via Phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) in a case-control design, whether bioenergetic deficits in autism spectrum disorders extend to the brain and muscle. Six cases with autism spectrum disorder with suspected mitochondrial dysfunction (age 6-18 years) and 6 age/sex-matched controls underwent (31)P magnetic resonance spectroscopy. The outcomes of focus were muscle resting phosphocreatine and intracellular pH as well as postexercise phosphocreatine recovery time constant and frontal brain phosphocreatine. Intracellular muscle pH was lower in each autism spectrum disorder case than their matched control (6/6, P = .03; P = .0048, paired t test). Muscle phosphocreatine (5/6), brain phosphocreatine (3/4), and muscle phosphocreatine recovery time constant (3/3) trends were in the predicted direction (not all participants completed each). This study introduces (31)P magnetic resonance spectroscopy as a noninvasive tool for assessment of mitochondrial function in autism spectrum disorder enabling bioenergetic assessment in brain and provides preliminary evidence suggesting that bioenergetic defects in cases with autism spectrum disorder are present in muscle and may extend to brain.

Orthostatic tremor, progressive external ophthalmoplegia, and Twinkle

IMPORTANCE

Orthostatic tremor (OT) is a high-frequency (13-18 Hz) leg tremor occurring in standing position. Orthostatic tremor has an unknown pathophysiologic mechanism. It is thought to be sporadic but siblings with OT from 3 unrelated families were reported. No mutations have been reported in OT. We describe a patient with OT carrying a C10orf2 TWINKLE mutation to highlight the possible association of OT with mitochondrial dysfunction and mutations in the mitochondrial replicative helicase Twinkle.

OBSERVATIONS

A man in his late 60s had ptosis and tremor on standing for 30 years, followed by development of progressive external ophthalmoplegia. Polygraphic recordings revealed an orthostatic synchronic tremor with 17.5-Hz frequency. Electromyography/nerve conduction studies showed evidence for a mild myopathy and associated mild axonal sensorimotor peripheral neuropathy. Muscle biopsy revealed ragged red fibers; mild cerebral atrophy was evident by magnetic resonance imaging. Molecular analysis revealed a novel heterozygous missense mutation at an evolutionarily conserved residue of the C10orf2 TWINKLE gene.

CONCLUSIONS AND RELEVANCE

Although the incidental association of OT and C10orf2 TWINKLE mutation is possible, the simultaneous onset of OT and eyelid ptosis at a much younger age than usually observed for OT raises the possibility of mitochondrial dysfunction and loss of mitochondrial DNA integrity in the pathogenesis of OT.

Automated methods for the analysis of skeletal muscle fiber size and metabolic type

It is of interest to quantify the size, shape, and metabolic subtype of skeletal muscle fibers in many areas of biomedical research. To do so, skeletal muscle samples are sectioned transversely to the length of the muscle and labeled for extracellular or membrane proteins to delineate the fiber boundaries and additionally for biomarkers related to function or metabolism. The samples are digitally photographed and the fibers "outlined" for quantification of fiber cross-sectional area (CSA) using pointing devices interfaced to a computer, which is tedious, prone to error, and can be nonobjective. Here, we review methods for characterizing skeletal muscle fibers and describe new automated techniques, which rapidly quantify CSA and biomarkers. We discuss the applications of these methods to the characterization of mitochondrial dysfunctions, which underlie a variety of human afflictions, and we present a novel approach, utilizing images from the online Human Protein Atlas to predict relationships between fiber-specific protein expression, function, and metabolism.

Effects of endotracheal intubation and surfactant on a 3-channel neonatal electroencephalogram

OBJECTIVE

To evaluate the effects of surfactant administration on the neonatal brain using 3-channel neonatal electroencephalography (EEG).

STUDY DESIGN

A prospective cohort of 30 infants had scalp electrodes placed to record brain waves using 3-channel EEG (Fp1-O1, C3-C4, and Fp2-O2). Sixty-second EEG epochs were collected from a 10-minute medication-free baseline, during premedication for endotracheal intubation, at surfactant administration, and at 10, 20, and 30 minutes after surfactant administration for amplitude comparisons. Oxygen saturation and heart rate were monitored continuously. Blood pressure and transcutaneous carbon dioxide were recorded every 5 minutes.

RESULTS

Eighteen of 29 infants (62%) exhibited brain wave suppression on EEG after surfactant administration (P ≤ .008). Four of those 18 infants did not receive premedication. Nine infants exhibited evidence of EEG suppression during endotracheal intubation, all of whom received premedication before intubation. Five infants had EEG suppression during endotracheal suctioning. Oxygen saturation, heart rate, and blood pressure were not independent predictors of brain wave suppression.

CONCLUSION

Eighteen of 29 intubated infants (62%) had evidence of brain wave suppression on raw EEG after surfactant administration. Nine patients had evidence of brief EEG suppression with endotracheal intubation alone, a finding not previously reported in neonates. Intubation and surfactant administration have the potential to alter cerebral function in neonates.

Fibroblast immuno-diagnosis of cytochrome oxidase (COX) deficiency in mitochondrial disease

We studied cytochrome c oxidase (COX) expression patterns in nuclear and mtDNA gene defects. Using quantitative immunocytochemical assay for COX, heteroplasmic staining was seen in MELAS patients with mtDNA mutations but similar staining variability was seen in control cell lines and nuclear gene defects. All fibroblast lines showed a wide variability in cell-to-cell COX I staining intensity. All 8 patient fibroblast lines had reduced COX staining on immunocytochemistry. In 6 lines reduced protein amount was seen on Western blotting and 7 had low COX activity. This study demonstrates that nuclear gene defects can produce a heteroplasmic appearance on immunocytochemistry.

Expanded clinical and molecular spectrum of guanidinoacetate methyltransferase (GAMT) deficiency

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by excessive amounts of guanidinoacetate in body fluids, deficiency of creatine in the brain, and presence of mutations in the GAMT gene. We present here 8 new patients with GAMT deficiency along with their clinical, biochemical and molecular data. The age at diagnosis of our patients ranges from 0 to 14 years. The age of onset of seizures usually ranges from infancy to 3 years. However, one of our patients developed seizures at age 5; progressing to myoclonic epilepsy at age 8 years and another patient has not developed seizures at age 17 years. Five novel mutations were identified: c.37ins26 (p.G13PfsX38), c.403G>T (p.D135Y), c.507_521dup15 (p.C169_S173dup), c.402C>G (p.Y134X) and c.610_611delAGinsGAA (p.R204EfsX63). Six patients had the c.327G>A (last nucleotide of exon 2) splice-site mutation which suggests that this is one of the most common mutations in the GAMT gene, second only to the known Portuguese founder mutation, c.59G>C (p.W20S). Our data suggests that the clinical presentation can be variable and the diagnosis may be overlooked due to unawareness of this disorder. Therefore, GAMT deficiency should be considered in the differential diagnosis of progressive myoclonic epilepsy as well as in unexplained developmental delay or regression with dystonia, even if the patient has no history of seizures. As more patients are reported, the prevalence of GAMT deficiency will become known and guidelines for prenatal diagnosis, newborn screening, presymptomatic testing and treatment, will need to be formulated.

Statin myopathy as a metabolic muscle disease

The etiology of statin myopathy remains unclear and concern about this toxicity is a leading reason that statins are underutilized. A number of observations suggest that this toxicity may be due to the metabolic effects of lipid-lowering in patients with minor muscle disorders. These patients have a high frequency of mutations for metabolic muscle diseases and often have depleted mitochondrial enzymes. Their exercise physiology and biopsy findings indicate reduced oxidation of fats and mitochondrial dysfunction. These subjects are often intolerant of other lipid-lowering therapies in addition to statins, which suggests that the myopathy is due to lipid-lowering itself more than a simple pharmacokinetic reaction to high statin levels. Altogether, these findings support the concept that statin myopathy is a metabolic muscle disease.

The in-depth evaluation of suspected mitochondrial disease

Mitochondrial disease confirmation and establishment of a specific molecular diagnosis requires extensive clinical and laboratory evaluation. Dual genome origins of mitochondrial disease, multi-organ system manifestations, and an ever increasing spectrum of recognized phenotypes represent the main diagnostic challenges. To overcome these obstacles, compiling information from a variety of diagnostic laboratory modalities can often provide sufficient evidence to establish an etiology. These include blood and tissue histochemical and analyte measurements, neuroimaging, provocative testing, enzymatic assays of tissue samples and cultured cells, as well as DNA analysis. As interpretation of results from these multifaceted investigations can become quite complex, the Diagnostic Committee of the Mitochondrial Medicine Society developed this review to provide an overview of currently available and emerging methodologies for the diagnosis of primary mitochondrial disease, with a focus on disorders characterized by impairment of oxidative phosphorylation. The aim of this work is to facilitate the diagnosis of mitochondrial disease by geneticists, neurologists, and other metabolic specialists who face the challenge of evaluating patients of all ages with suspected mitochondrial disease.

Pitfalls in the denaturing high-performance liquid chromatography analysis of mitochondrial DNA mutation

Denaturing high-performance liquid chromatography (DHPLC) purification of heteroduplexes has been reported as a method to increase sensitivity of the detection of low-level heteroplasmy by DNA sequencing, and DHPLC profiling has been suggested as a method to allow the correlation of a characteristic chromatographic profile with a specific sequence alteration. Herein we report pitfalls associated with the use of DHPLC for these purposes. We show that the purified heteroduplex fraction does not contain a 50:50 mix of wild-type and mutant DNA in DNA samples containing low-level mutations, and that with a commonly used protocol, DNA sequencing gave false negative results at the 1% mutation level, potentially leading to misdiagnosis. We improved the protocol to detect low levels of mutations and evaluated the sensitivity of DNA sequencing in the detection of mutation in these fractions. We also studied the DHPLC profiles of several mutations in the tRNALeu(UUR) region of mitochondrial DNA and found a characteristic profile in only one of five mutants tested, whereas four other mutants showed identical chromatographic profiles.

Mitochondrial disease: a practical approach for primary care physicians

Notorious variability in the presentation of mitochondrial disease in the infant and young child complicates its clinical diagnosis. Mitochondrial disease is not a single entity but, rather, a heterogeneous group of disorders characterized by impaired energy production due to genetically based oxidative phosphorylation dysfunction. Together, these disorders constitute the most common neurometabolic disease of childhood with an estimated minimal risk of developing mitochondrial disease of 1 in 5000. Diagnostic difficulty results from not only the variable and often nonspecific presentation of these disorders but also from the absence of a reliable biomarker specific for the screening or diagnosis of mitochondrial disease. A simplified and standardized approach to facilitate the clinical recognition of mitochondrial disease by primary physicians is needed. With this article we aimed to improve the clinical recognition of mitochondrial disease by primary care providers and empower the generalist to initiate appropriate baseline diagnostic testing before determining the need for specialist referral. This is particularly important in light of the international shortage of metabolism specialists to comprehensively evaluate this large and complex disease population. It is hoped that greater familiarity among primary care physicians with the protean manifestations of mitochondrial disease will facilitate the proper diagnosis and management of this growing cohort of pediatric patients who present across all specialties.

Pontine tegmental cap dysplasia: a novel brain malformation with a defect in axonal guidance

Four unrelated children are described with an identical brainstem and cerebellar malformation on MRI. The key findings are: vermal hypoplasia, subtotal absence of middle cerebellar peduncles, flattened ventral pons, vaulted pontine tegmentum, molar tooth aspect of the pontomesencephalic junction and absent inferior olivary prominence. Peripheral hearing impairment is present in all. Variable findings are: horizontal gaze palsy (1/4), impaired swallowing (2/4), facial palsy (3/4), bilateral sensory trigeminal nerve involvement (1/4), ataxia (2/4). Bony vertebral anomalies are found in 3/4. Additional MR studies in one patient using diffusion tensor imaging (DTI) with colour coding and fibre tracking revealed an ectopic transverse fibre bundle at the site of the pontine tegmentum and complete absence of transverse fibres in the ventral pons. The combined findings indicate an embryonic defect in axonal growth and guidance. Phenotypic analogy to mice with homozygous inactivation of Ntn1 encoding the secreted axonal guidance protein netrin1, or Dcc encoding its receptor Deleted in Colorectal Cancer led us to perform sequence analysis of NTN1 and DCC in all the patients. No pathogenic mutations were found. For the purpose of description the name 'pontine tegmental cap dysplasia' (PTCD) is proposed for the present malformation, referring to its most distinguishing feature on routine MRI.

The evidence basis for coenzyme Q therapy in oxidative phosphorylation disease

The evidence supporting a treatment benefit for coenzyme Q10 (CoQ10) in primary mitochondrial disease (mitochondrial disease) whilst positive is limited. Mitochondrial disease in this context is defined as genetic disease causing an impairment in mitochondrial oxidative phosphorylation (OXPHOS). There are no treatment trials achieving the highest Level I evidence designation. Reasons for this include the relative rarity of mitochondrial disease, the heterogeneity of mitochondrial disease, the natural cofactor status and easy 'over the counter availability' of CoQ10 all of which make funding for the necessary large blinded clinical trials unlikely. At this time the best evidence for efficacy comes from controlled trials in common cardiovascular and neurodegenerative diseases with mitochondrial and OXPHOS dysfunction the etiology of which is most likely multifactorial with environmental factors playing on a background of genetic predisposition. There remain questions about dosing, bioavailability, tissue penetration and intracellular distribution of orally administered CoQ10, a compound which is endogenously produced within the mitochondria of all cells. In some mitochondrial diseases and other commoner disorders such as cardiac disease and Parkinson's disease low mitochondrial or tissue levels of CoQ10 have been demonstrated providing an obvious rationale for supplementation. This paper discusses the current state of the evidence supporting the use of CoQ10 in mitochondrial disease.

Quantitative Mitochondrial DNA Mutation Analysis by Denaturing HPLC

Background: In recent years, denaturing HPLC (DHPLC) has been widely used to screen the whole mitochondrial genome or specific regions of the genome for DNA mutations. The quantification and mathematical modeling of DHPLC results is, however, underexplored.

Methods: We generated site-directed mutants containing some common mutations in the mitochondrial DNA (mtDNA) tRNA(leu) region with different mutation loads and used PCR to amplify the gene segment of interest in these mutants. We then performed restriction digestion followed by slow reannealing to induce heteroduplex formation and analyzed the samples by use of DHPLC.

Results: We observed a quadratic relationship between the heteroduplex peak areas and mutant loads, consistent with the kinetics of heteroduplex formation reported by others. This was modeled mathematically and used to quantify mtDNA mutation load. The method was able to detect a mutation present in a concentration as low as 1% and gave reproducible measurements of the mutations in the range of 2.5%–97.5%.

Conclusion: The quantitative DHPLC assay is well suited for simultaneous detection and quantification of DNA mutations.

Normal platelet mitochondrial complex I activity in Huntington's disease

Two small case series of platelet mitochondrial complex I activity assays in Huntington's Disease (HD) report discrepant results. We measured platelet complex I and complex I/III activity in 21 subjects with early gene-positive HD and 14 age-matched controls. The 21 participants with HD that we studied are greater than the total of 16 in the two previously published of platelet ETS activity in HD. Reductions > 10% were excluded with 80% confidence. A systemic defect in complex I activity is not present in early HD when striatal neuronal degeneration is already present.

Statin myotoxicity is associated with changes in the cardiopulmonary function

The mechanism of the muscle toxicity associated with lipid-lowering therapy remains obscure. Pathological and biochemical findings in patients with statin myotoxicity suggest impaired fatty acid oxidation. Exhaled gas analysis can be used to assess substrate utilization including fatty acid oxidation. In order to determine if muscle toxicity due to lipid-lowering therapy might be related to abnormalities in lipid oxidation, exhaled gas analysis was performed in the fasted state on 11 patients subsequent to statin-associated myositis reactions. Results were compared to those of 16 normal controls who were measured both on and off statin therapy. Post-myositis patients showed a depressed anaerobic threshold (AT) (P=0.009) compared to controls while age-adjusted maximal oxygen consumption (VO2max) and ventilatory efficiency (VE/VCO2) were not significantly different. The fasting respiratory exchange ratio (RER) of post-myositis patients off statins was abnormally increased (P=0.00001) as was their S1-slope (P=0.023). Controls demonstrated a significant increase in their RER while taking statins consistent with decreased lipid oxidation (P <0.00001). These findings suggest that abnormal lipid oxidation in certain patients may predispose them to the myotoxicity caused by lipid-lowering therapies.

Chronic treatment of mitochondrial disease patients with dichloroacetate

Clinical features are reported for 37 patients with various mitochondrial disorders, treated with sodium dichloroacetate (DCA) for 3 weeks to 7 years (mean 3.25 years) at 11-50 mg/kg/day (34.6+/-13.1) in an open-label format. DCA pharmacokinetics showed half-times approximately 86 min for the first intravenous dose of 50 mg/kg, 3.2 h for a subsequent intravenous dose 4-6 h later, and 11 h after continued oral dosing of 12.5-25 mg/kg twice daily. Basal blood and CSF lactate (mean values at entry 29.6 and 46.8 mg/dL, respectively) decreased at 3 months (to 18.1 and 34.2, respectively) and 12 months (to 17.7 and 33.1, respectively). There was some attenuation of the blood lactate response to oral fructose but not glucose, although the baseline lactate was lower with DCA. A standardized neurologic inventory showed stabilization or improvement over one year. The subjective impression of overall disease course was worsening in 21.6%, improvement in 48.6%, and no discernable effect in 29.7%. Among 8 patients who had 17 stroke-like events in 0.25-5 years prior to study entry, there were a total of 2 events over 3-6 years of treatment. In two cases institution of DCA resulted in dramatic relief of severe headaches which had been refractory to narcotics. Given variability of symptoms and limited understanding of natural history of mitochondrial disease, it is difficult to determine the efficacy of DCA in this open-label study, but there did appear to be some cases in which there were at least temporary benefits.

The role of methionine in ethylmalonic encephalopathy with petechiae

BACKGROUND

Among patients with ethylmalonic aciduria, a subgroup with encephalopathy, petechial skin lesions, and often death in infancy is distinct from those with short-chain acyl-coenzyme A dehydrogenase deficiency or multiple acyl-coenzyme A dehydrogenase deficiency. The nature of the molecular defect in this subgroup is unknown, and the source of the ethylmalonic acid has been unclear.

OBJECTIVE

To determine whether the administration of candidate amino acids increased the excretion of ethylmalonic acid.

DESIGN

Examination of patterns of organic acids excreted in the urine before and following loading doses of isoleucine and methionine.

SETTING

General clinical research center.

PATIENT

An infant with ethylmalonic aciduria, global developmental delay, acrocyanosis, and intermittent showers of petechiae.

MAIN OUTCOME MEASURE

Excretion of ethylmalonic acid in the urine.

RESULTS

Loading with methionine increased the excretion of ethylmalonic acid, whereas loading with isoleucine did not. Restriction of the dietary intake of methionine decreased ethylmalonic acid excretion.

CONCLUSION

In ethylmalonic acid encephalopathy with petechiae, methionine is a precursor of ethylmalonic acid.

Statin-associated myopathy with normal creatine kinase levels

BACKGROUND

Muscle symptoms in patients who are treated with statins and have normal creatine kinase levels are not well understood.

OBJECTIVE

To report biopsy-confirmed myopathy and normal creatine kinase levels associated with statin use.

DESIGN

Case reports from preliminary analysis of an ongoing clinical trial.

SETTING

Clinical research center in a community hospital.

PATIENTS

Four patients with muscle symptoms that developed during statin therapy and reversed during placebo use.

MEASUREMENTS

1) Patients' ability to identify blinded statin therapy and 2) standard measures of functional capacity and muscle strength.

RESULTS

All four patients repeatedly distinguished blinded statin therapy from placebo. Strength testing confirmed weakness during statin therapy that reversed during placebo use. Muscle biopsies showed evidence of mitochondrial dysfunction, including abnormally increased lipid stores, fibers that did not stain for cytochrome oxidase activity, and ragged red fibers. These findings reversed in the three patients who had repeated biopsy when they were not receiving statins. Creatine kinase levels were normal in all four patients despite the presence of significant myopathy.

CONCLUSION

Some patients who develop muscle symptoms while receiving statin therapy have demonstrable weakness and histopathologic findings of myopathy despite normal serum creatine kinase levels.

Pyruvate carboxylase deficiency--insights from liver transplantation

Pyruvate carboxylase deficiency, complex form, presents in early infancy with lethal metabolic acidosis, resulting from ketoacidosis and lactic acidemia. Renal tubular acidosis, hyperammonemia, and citrullinemia complete the picture. In an infant with this disease, large amounts of glucose ameliorated the ketoacidosis, but worsened the lactic acidosis. Orthotopic hepatic transplantation completely reversed the ketoacidosis and the renal tubular abnormality and ameliorated the lactic acidemia. Concentrations of glutamine in cerebrospinal fluid were low and did not improve with liver transplantation.

Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study

OBJECTIVE

To quantify developmental abnormalities in cerebral and cerebellar volume in autism.

METHODS

The authors studied 60 autistic and 52 normal boys (age, 2 to 16 years) using MRI. Thirty autistic boys were diagnosed and scanned when 5 years or older. The other 30 were scanned when 2 through 4 years of age and then diagnosed with autism at least 2.5 years later, at an age when the diagnosis of autism is more reliable.

RESULTS

Neonatal head circumferences from clinical records were available for 14 of 15 autistic 2- to 5-year-olds and, on average, were normal (35.1 +/- 1.3 cm versus clinical norms: 34.6 +/- 1.6 cm), indicative of normal overall brain volume at birth; one measure was above the 95th percentile. By ages 2 to 4 years, 90% of autistic boys had a brain volume larger than normal average, and 37% met criteria for developmental macrencephaly. Autistic 2- to 3-year-olds had more cerebral (18%) and cerebellar (39%) white matter, and more cerebral cortical gray matter (12%) than normal, whereas older autistic children and adolescents did not have such enlarged gray and white matter volumes. In the cerebellum, autistic boys had less gray matter, smaller ratio of gray to white matter, and smaller vermis lobules VI-VII than normal controls.

CONCLUSIONS

Abnormal regulation of brain growth in autism results in early overgrowth followed by abnormally slowed growth. Hyperplasia was present in cerebral gray matter and cerebral and cerebellar white matter in early life in patients with autism.

Nerve conduction changes in patients with mitochondrial diseases treated with dichloroacetate

Serial measurements of nerve conduction velocities and amplitudes were performed in 27 patients with congenital lactic acidemia over 1 year of sodium dichloroacetate (DCA) administration. Patients were treated with oral thiamine (100 mg) and DCA (initial dose of 50 mg/kg) daily. Nerve conduction velocity and response amplitude were measured in the median, radial, tibial, and sural nerves at 0, 3, 6, and 12 months, and plasma DCA pharmacokinetics were measured at 3 and 12 months. Baseline electrophysiologic parameters in this population were generally below normal but as a group were within 2 standard deviations of normal means. Although symptoms of neuropathy were reported by only three patients or their families, nerve conduction declined in 12 patients with normal baseline studies, and worsening of nerve conduction occurred in the two who had abnormalities at baseline. Peripheral neuropathy appears to be a common side effect during chronic DCA treatment, even with coadministration of oral thiamine. Nerve conduction should be monitored during DCA treatment.

A comparison of genetic mitochondrial disease and nucleoside analogue toxicity. Does fetal nucleoside toxicity underlie reports of mitochondrial disease in infants born to women treated for HIV infection?

Recent reports of mitochondrial disease in infants whose mothers were treated in pregnancy with nucleoside analogues are of concern. Chronic nucleoside analogue treatment of adults has long been known to cause mitochondrial DNA depletion with the risk of multisystem disease. Combination nucleoside analogue treatment regimens may have the greatest risk of toxicity. This paper briefly presents the underlying biochemical etiologies and phenotypes of some common genetic mitochondrial diseases in order to provide a comparison with reports of infant toxicity. A standardized method for the diagnosis and evaluation of mitochondrial disease is discussed. A hypothesis, with predictions of the effects of antenatal nucleoside analogue treatment on the fetus, is presented and future directions for research on this problem are suggested.

Autism associated with the mitochondrial DNA G8363A transfer RNA(Lys) mutation

We report a family with a heterogeneous group of neurologic disorders associated with the mitochondrial DNA G8363A transfer ribonucleic acid (RNA)Lys mutation. The phenotype of one child in the family was consistent with autism. During his second year of life, he lost previously acquired language skills and developed marked hyperactivity with toe-walking, abnormal reciprocal social interaction, stereotyped mannerisms, restricted interests, self-injurious behavior, and seizures. Brain magnetic resonance imaging (MRI) and repeated serum lactate studies were normal. His older sister developed signs of Leigh syndrome with progressive ataxia, myoclonus, seizures, and cognitive regression. Her laboratory studies revealed increased MRI T2-weighted signal in the putamen and posterior medulla, elevated lactate in serum and cerebrospinal fluid, and absence of cytochrome c oxidase staining in muscle histochemistry. Molecular analysis in her revealed the G8363A mutation of the mitochondrial transfer RNA(Lys) gene in blood (82% mutant mitochondrial DNA) and muscle (86%). The proportions of mutant mitochondrial DNA from her brother with autism were lower (blood 60%, muscle 61%). It is likely that the origin of his autism phenotype is the pathogenic G8363A mitochondrial DNA mutation. This observation suggests that certain mitochondrial point mutations could be the basis for autism in some individuals.

Kearns-Sayre syndrome presenting as 2-oxoadipic aciduria

A patient with 2-oxoadipic aciduria and 2-aminoadipic aciduria presented at 2 years of age with manifestations typical of organic acidemia, episodes of ketosis and acidosis, progressive to coma. This resolved and the key metabolites disappeared from the urine and blood. At 9 years of age she developed typical Kearns-Sayre syndrome with complete heart block, retinopathy, and ophthalmoplegia. Southern blot revealed a deletion in the mitochondrial genome.

Sensitive assay for mitochondrial DNA polymerase gamma

BACKGROUND

The mitochondrial DNA polymerase gamma is the principal polymerase required for mitochondrial DNA replication. Primary or secondary deficiencies in the activity of DNA polymerase gamma may lead to mitochondrial DNA depletion. We describe a sensitive and robust clinical assay for this enzyme.

METHODS

The assay was performed on mitochondria isolated from skeletal muscle biopsies. High-molecular weight polynucleotide reaction products were captured on ion-exchange paper, examined qualitatively by autoradiography, and quantified by scintillation counting.

RESULTS

Kinetic analysis of DNA polymerase gamma by this method showed a K(m) for dTTP of 1.43 micromol/L and a K(i) for azidothymidine triphosphate of 0.861 micromol/L. The assay was linear from 0.1 to 2 microgram of mitochondrial protein. The detection limit was 30 units (30 fmol dTMP incorporated in 30 min). The linear dynamic range was three orders of magnitude; 30-30 000 units. Imprecision (CV) was 6.4% within day and 12% between days. Application of this assay to a mixed population of 38 patients referred for evaluation of mitochondrial disease revealed a distribution with a range of 0-2506 U/microgram, reflecting extensive biologic variation among patients with neuromuscular disease.

CONCLUSION

This assay provides a useful adjunct to current laboratory methods for the evaluation of patients with suspected mitochondrial DNA depletion syndromes.

Sensitive Assay for Mitochondrial DNA Polymerase γ

Background: The mitochondrial DNA polymerase γ is the principal polymerase required for mitochondrial DNA replication. Primary or secondary deficiencies in the activity of DNA polymerase γ may lead to mitochondrial DNA depletion. We describe a sensitive and robust clinical assay for this enzyme.

Methods: The assay was performed on mitochondria isolated from skeletal muscle biopsies. High-molecular weight polynucleotide reaction products were captured on ion-exchange paper, examined qualitatively by autoradiography, and quantified by scintillation counting.

Results: Kinetic analysis of DNA polymerase γ by this method showed a Km for dTTP of 1.43 μmol/L and a Ki for azidothymidine triphosphate of 0.861 μmol/L. The assay was linear from 0.1 to 2 μg of mitochondrial protein. The detection limit was 30 units (30 fmol dTMP incorporated in 30 min). The linear dynamic range was three orders of magnitude; 30–30 000 units. Imprecision (CV) was 6.4% within day and 12% between days. Application of this assay to a mixed population of 38 patients referred for evaluation of mitochondrial disease revealed a distribution with a range of 0–2506 U/μg, reflecting extensive biologic variation among patients with neuromuscular disease.

Conclusion: This assay provides a useful adjunct to current laboratory methods for the evaluation of patients with suspected mitochondrial DNA depletion syndromes.

Mitochondrial DNA polymerase gamma deficiency and mtDNA depletion in a child with Alpers' syndrome

Deficiency of mitochondrial DNA polymerase gamma activity was found in a patient with mtDNA depletion and Alpers' syndrome. Metabolic evaluation revealed fasting hypoglycemia, dicarboxylic aciduria, and reduced activity of the electron transport chain in skeletal muscle. The patient died in early childhood of fulminant hepatic failure, refractory epilepsy, lactic acidemia, and coma. mtDNA content was 30% of normal in skeletal muscle and 25% in the liver. The activity of mtDNA polymerase gamma was undetectable.

A possible role of coenzyme Q10 in the etiology and treatment of Parkinson's disease

Parkinson's disease (PD) is a degenerative neurological disorder. Recent studies have demonstrated reduced activity of complex I of the electron transport chain in brain and platelets from patients with PD. Platelet mitochondria from parkinsonian patients were found to have lower levels of coenzyme Q10 (CoQ10) than mitochondria from age/sex-matched controls. There was a strong correlation between the levels of CoQ10 and the activities of complexes I and II/III. Oral CoQ10 was found to protect the nigrostriatal dopaminergic system in one-year-old mice treated with MPTP, a toxin injurious to the nigrostriatal dopaminergic system. We further found that oral CoQ10 was well absorbed in parkinsonian patients and caused a trend toward increased complex I activity. These data suggest that CoQ10 may play a role in cellular dysfunction found in PD and may be a potential protective agent for parkinsonian patients.

Analysis of organic acids, amino acids, and carnitine in dogs with lipid storage myopathy

Abnormal accumulations of lipid droplets, localized predominantly in histochemical type 1 fibers, were observed in fresh frozen sections of muscle biopsies from 25 dogs with myalgia, weakness, and muscle atrophy. Compared to controls, lactic acidemia, hyperalaninemia, lactic and pyruvic aciduria, variably increased urinary excretion of carnitine esters, and muscle carnitine deficiency were present. These findings support a metabolic block in oxidative metabolism resulting in lactic acidemia in dogs with lipid storage myopathy.

Absorption, tolerability, and effects on mitochondrial activity of oral coenzyme Q10 in parkinsonian patients

We report a pilot study of three oral doses of coenzyme Q10 (CoQ10) (200 mg administered two, three, or four times per day for 1 month) in 15 subjects with Parkinson's disease. Oral CoQ10 caused a substantial increase in the plasma CoQ10 level. It was well tolerated, but at the highest dose (200 mg four times per day) mild, transient changes in the urine were noted. CoQ10 did not change the mean score on the motor portion of the Unified Parkinson's Disease Rating Scale. There was a trend toward an increase in complex I activity in the subjects.