Pyruvate dehydrogenase-e1α deficiency presenting as recurrent demyelination: an unusual presentation and a novel mutation

Recurrent Sensory-Motor Neuropathy Mimicking CIDP as Predominant Presentation of PDH Deficiency

INTRODUCTION

 Pyruvate dehydrogenase complex (PDH) deficiency (Online Mendelian Inheritance in Man # 312170) is a relatively common mitochondrial disorder, caused by mutations in the X-linked PDHA1 gene and presenting with a variable phenotypic spectrum, ranging from severe infantile encephalopathy to milder chronic neurological disorders.Isolated peripheral neuropathy as predominant clinical presentation is uncommon.

RESULTS

 We report on a patient, now 21 years old, presenting at the age of 2 years with recurrent symmetric weakness as first symptom of a PDH deficiency. Neurophysiological evaluation proving a sensory-motor polyneuropathy with conduction blocks and presence of elevated cerebrospinal fluid proteins, suggested a chronic inflammatory demyelinating polyneuropathy. The evidence of high serum lactate and the alterations in oxidative metabolism in muscle biopsy pointed toward the final diagnosis. After starting nutritional supplements, no further episodes occurred. A hemizygous mutation in PDHA1 (p.Arg88Cys) was identified. This mutation has been previously described in five patients with a similar phenotype. A three-dimensional reconstruction demonstrated that mutations affecting this arginine destabilize the interactions between the subunits of the E1 complex.

CONCLUSION

 We summarize the clinical and genetic characteristics of one patient with PDH deficiency presenting isolated peripheral nervous system involvement. This study highlights that the diagnosis of PDH deficiency should be considered in children with unexplained peripheral neuropathy, even with features suggestive of acquired forms, especially in case of early onset and limited response to treatment. A simple analysis of lactic acid could help to target the diagnosis.In addition, we suggest that the residue Arg88 is the most frequently involved in this specific phenotype of PDH deficiency.

Neurodegenerative Disorder Risk in Krabbe Disease Carriers

Krabbe disease (KD) is a rare autosomal recessive disorder caused by mutations in the galactocerebrosidase gene (GALC). Defective GALC causes aberrant metabolism of galactolipids present almost exclusively in myelin, with consequent demyelinization and neurodegeneration of the central and peripheral nervous system (NS). KD shares some similar features with other neuropathies and heterozygous carriers of GALC mutations are emerging with an increased risk in developing NS disorders. In this work, we set out to identify possible variations in the proteomic profile of KD-carrier brain to identify altered pathways that may imbalance its homeostasis and that may be associated with neurological disorders. The differential analysis performed on whole brains from 33-day-old twitcher (galc ^−/−), heterozygous (galc ^+/−), and wild-type mice highlighted the dysregulation of several multifunctional factors in both heterozygous and twitcher mice. Notably, the KD-carrier mouse, despite its normal phenotype, presents the deregulation of vimentin, receptor of activated protein C kinase 1 (RACK1), myelin basic protein (MBP), 2′,3′-cyclic-nucleotide 3′-phosphodiesterase (CNP), transitional endoplasmic reticulum ATPase (VCP), and N-myc downstream regulated gene 1 protein (NDRG1) as well as changes in the ubiquitinated-protein pattern. Our findings suggest the carrier may be affected by dysfunctions classically associated with neurodegeneration: (i) alteration of (mechano) signaling and intracellular trafficking, (ii) a generalized affection of proteostasis and lipid metabolism, with possible defects in myelin composition and turnover, and (iii) mitochondrion and energy supply dysfunctions.

To be, or not to be… Guillain-Barré Syndrome

Guillain-Barré Syndrome (GBS) is currently the most frequent cause of acute flaccid paralysis on a global scale, being an autoimmune disorder wherein demyelination of the peripheral nerves occurs. Its main clinical features are a symmetrical ascending muscle weakness with reduced osteotendinous reflexes and variable sensory involvement. GBS most commonly occurs after an infection, especially viral (including COVID-19), but may also transpire after immunization with certain vaccines or in the development of specific malignancies. Immunoglobulins, plasmapheresis, and glucocorticoids represent the principal treatment modalities, however patients with severe disease progression may require supportive therapy in an intensive care unit. Due to its symptomology, which overlaps with numerous neurological and infectious illnesses, the diagnosis of GBS may often be misattributed to pathologies that are essentially different from this syndrome. Moreover, many of these require specific treatment methods distinct to those recommended for GBS, in lack of which the prognosis of the patient is drastically affected. Such diseases include exposure to toxins either environmental or foodborne, central nervous system infections, metabolic or serum ion alterations, demyelinating pathologies, or even conditions amenable to neurosurgical intervention. This extensive narrative review aims to systematically and comprehensively tackle the most notable and challenging differential diagnoses of GBS, emphasizing on the clinical discrepancies between the diseases, the appropriate paraclinical investigations, and suitable management indications.

Novel presentations associated with a PDHA1 variant - Alternating hemiplegia in Hemizygote proband and Guillain Barre Syndrome in Heterozygote mother

We report a 5-year-old male with a PDHA1 variant who presented with alternating hemiplegia of childhood and later developed developmental regression, basal ganglia injury and episodic lactic acidosis. Enzyme assay in lymphocytes confirmed a diagnosis of Pyruvate Dehydrogenase Complex (PDC) deficiency. His mother who was heterozygous for the same variant suffered from ophthalmoplegia, chronic migraine and developed flaccid paralysis at 36 years of age. PDHA1 is the most common genetic cause of PDC deficiency and presents with a myriad of neurological phenotypes including neonatal form with lactic acidosis, non-progressive infantile encephalopathy, Leigh syndrome subtype and intermittent ataxia. The presentations in our 2 patients contribute to the clinical heterogeneity of this neurogenetic condition.

Serial Magnetic Resonance Imaging (MRI) in Pyruvate Dehydrogenase Complex Deficiency

OBJECTIVES

To report 2 additional cases of pyruvate dehydrogenase complex deficiency with reversible deep gray matter lesions following initiation of ketogenic diet and to perform a literature review of serial imaging in patients with pyruvate dehydrogenase complex.

METHODS

Clinical data on 3 previously unpublished cases of patients with pyruvate dehydrogenase complex deficiency and with serial magnetic resonance imagings (MRIs) before and after institution of ketogenic diet were reported. A systematic literature review was performed to search for published cases of patients with confirmed pyruvate dehydrogenase complex deficiency who underwent serial MRIs.

RESULTS

The 3 subjects in this series demonstrated clinical improvement on ketogenic diet. Two subjects showed reversal of some brain lesions on repeat MRI following initiation of ketogenic diet. Of the 21 published cases with serial MRIs, 13 patients underwent some form of treatment, and of this smaller subset 4 patients had repeat MRIs that showed definitive improvement. In both our described cases and those published in the literature, improvement occurred in lesions in the basal ganglia.

CONCLUSIONS

In patients with pyruvate dehydrogenase complex deficiency, basal ganglia lesions on MRI are reversible with treatment in some cases and could serve as a biomarker for measuring response to treatment.

Quantitative Proteomic and Network Analysis of Differentially Expressed Proteins in PBMC of Friedreich's Ataxia (FRDA) Patients

Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by an expanded (GAA) trinucleotide repeat in the FXN gene. The extended repeats expansion results in reduced transcription and, thereby, decreased expression of the mitochondrial protein, frataxin. Given the ongoing drug trials, identification of reliable and easily accessible biomarkers for monitoring disease progression and therapeutic intervention is a foremost requirement. In this study, comparative proteomic profiling of PBMC proteins from FRDA patients and age- and gender-matched healthy controls was done using 2D-Differential in-Gel Electrophoresis (2D-DIGE). Protein–protein interaction (PPI) was analyzed using BioGRID and STRING pathway analysis tools. Using biological variance analysis (BVA) and LC/MS, we found eight differentially expressed proteins with fold change ≥1.5; p ≤ 0.05. Based on their cellular function, the identified proteins showed a strong pathological role in neuroinflammation, cardiomyopathy, compromised glucose metabolism, and iron transport, which are the major clinical manifestations of FRDA. Protein–protein network analysis of differentially expressed proteins with frataxin further supports their involvement in the pathophysiology of FRDA. Considering their crucial role in the cardiac and neurological complications, respectively, the two down-regulated proteins, actin α cardiac muscle 1 (ACTC1) and pyruvate dehydrogenase E1 component subunit β (PDHE1), are suggested as potential prognostic markers for FRDA.

Ketogenic diet in pyruvate dehydrogenase complex deficiency: short- and long-term outcomes

OBJECTIVES

Our aime was to study the short- and long-term effects of ketogenic diet on the disease course and disease-related outcomes in patients with pyruvate dehydrogenase complex deficiency, the metabolic factors implicated in treatment outcomes, and potential safety and compliance issues.

METHODS

Pediatric patients diagnosed with pyruvate dehydrogenase complex deficiency in Sweden and treated with ketogenic diet were evaluated. Study assessments at specific time points included developmental and neurocognitive testing, patient log books, and investigator and parental questionnaires. A systematic literature review was also performed.

RESULTS

Nineteen patients were assessed, the majority having prenatal disease onset. Patients were treated with ketogenic diet for a median of 2.9 years. All patients alive at the time of data registration at a median age of 6 years. The treatment had a positive effect mainly in the areas of epilepsy, ataxia, sleep disturbance, speech/language development, social functioning, and frequency of hospitalizations. It was also safe-except in one patient who discontinued because of acute pancreatitis. The median plasma concentration of ketone bodies (3-hydroxybutyric acid) was 3.3 mmol/l. Poor dietary compliance was associated with relapsing ataxia and stagnation of motor and neurocognitive development. Results of neurocognitive testing are reported for 12 of 19 patients.

CONCLUSION

Ketogenic diet was an effective and safe treatment for the majority of patients. Treatment effect was mainly determined by disease phenotype and attainment and maintenance of ketosis.

Ketogenic diet and childhood neurological disorders other than epilepsy: an overview

INTRODUCTION

In the last years, ketogenic diet (KD) has been experimentally utilized in various childhood neurologic disorders such as mitochondriopathies, alternating hemiplegia of childhood (AHC), brain tumors, migraine, and autism spectrum disorder (ASD). The aim of this review is to analyze how KD can target these different medical conditions, highlighting possible mechanisms involved. Areas covered: We have conducted an analysis on literature concerning KD use in mitochondriopathies, AHC, brain tumors, migraine, and ASD. Expert commentary: The role of KD in reducing seizure activity in some mitochondriopathies and its efficacy in pyruvate dehydrogenase deficiency is known. Recently, few cases suggest the potentiality of KD in decreasing paroxysmal activity in children affected by AHC. A few data support its potential use as co-adjuvant and alternative therapeutic option for brain cancer, while any beneficial effect of KD on migraine remains unclear. KD could improve cognitive and social skills in a subset of children with ASD.

The spectrum of pyruvate oxidation defects in the diagnosis of mitochondrial disorders

Pyruvate oxidation defects (PODs) are among the most frequent causes of deficiencies in the mitochondrial energy metabolism and represent a substantial subset of classical mitochondrial diseases. PODs are not only caused by deficiency of subunits of the pyruvate dehydrogenase complex (PDHC) but also by various disorders recently described in the whole pyruvate oxidation route including cofactors, regulation of PDHC and the mitochondrial pyruvate carrier. Our own patients from 2000 to July 2014 and patients identified by a systematic survey of the literature from 1970 to July 2014 with a pyruvate oxidation disorder and a genetically proven defect were included in the study (n=628). Of these defects 74.2% (n=466) belong to PDHC subunits, 24.5% (n=154) to cofactors, 0.5% (n=3) to PDHC regulation and 0.8% (n=5) to mitochondrial pyruvate import. PODs are underestimated in the field of mitochondrial diseases because not all diagnostic centres include biochemical investigations of PDHC in their routine analysis. Cofactor and transport defects can be missed, if pyruvate oxidation is not measured in intact mitochondria routinely. Furthermore deficiency of the X-chromosomal PDHA1 can be biochemically missed depending on the X-inactivation pattern. This is reflected by an increasing number of patients diagnosed recently by genetic high throughput screening approaches. PDHC deficiency including regulation and import affect mainly the glucose dependent central and peripheral nervous system and skeletal muscle. PODs with combined enzyme defects affect also other organs like heart, lung and liver. The spectrum of clinical presentation of PODs is still expanding. PODs are a therapeutically interesting group of mitochondrial diseases since some can be bypassed by ketogenic diet or treated by cofactor supplementation. PDHC kinase inhibition, chaperone therapy and PGC1α stimulation is still a matter of further investigations.

Therapeutic strategies for mitochondrial disorders

OBJECTIVES

There is currently no curative therapy for mitochondrial disorders, although symptomatic measures can be highly effective and greatly improve the quality of life and outcome of these patients. This review highlights potential strategies for the therapeutic management of mitochondrial disorders.

METHODS

Data for this review were identified by searches of MEDLINE, Current Contents, using various relevant search terms.

RESULTS

Strategies to establish a therapeutic regimen aim to enhance respiratory chain function, eliminate noxious compounds, shift the heteroplasmy rate, alter mitochondrial dynamics, transfer cytoplasm, and promote gene therapy. Symptomatic measures rely on drugs (e.g., antiepileptics), avoidance of mitochondrion-toxic agents, substitution of blood cells, hemodialysis, invasive measures (such as a pacemaker), surgery (e.g., ptosis correction), physiotherapy, speech therapy, occupational therapy, dietary measures (e.g., ketogenic diet, anaplerotic diet), and the avoidance of mitochondrion-toxic agents (e.g., ozone). With the increasing awareness of mitochondrial disorders, the number of treatment studies is growing and its quality is improving. If high quality studies (high Jadad score) yield statistical significance for end points, a treatment is more reliable than with lower quality studies.

CONCLUSIONS

Despite the lack of a proven treatment for mitochondrial disorders, a nihilistic attitude toward treatment is not justified. A number of studies are seeking targeted therapies, and highly effective symptomatic measures are available.