Amino acid ratio combinations as biomarkers for discriminating patients with pyruvate dehydrogenase complex deficiency from other inborn errors of metabolism.

BACKGROUND: Pyruvate dehydrogenase complex deficiency (PDCD) is a mitochondrial neurometabolic disorder of energy deficit, with incidence of about 1 in 42,000 live births annually in the USA. The median and mean ages of diagnosis of PDCD are about 12 and 31 months, respectively. PDCD is a major cause of primary lactic acidosis with concomitant elevation in blood alanine (Ala) and proline (Pro) concentrations depending on phenotypic severity. Alanine/Leucine (Ala/Leu) ≥4.0 and Proline/Leucine (Pro/Leu) ≥3.0 combination cutoff from dried blood spot specimens was used as a biomarker for early identification of neonates/infants with PDCD. Further investigations were needed to evaluate the sensitivity (SN), specificity (SP), and clinical utility of such amino acid (AA) ratio combination cutoffs in discriminating PDCD from other inborn errors of metabolism (IEM) for early identification of such patients. METHODS: We reviewed medical records of patients seen at UPMC in the past 11 years with molecularly or enzymatically confirmed diagnosis. We collected plasma AA analysis data from samples prior to initiation of therapeutic interventions such as total parenteral nutrition and/or ketogenic diet. Conditions evaluated included organic acidemias, primary mitochondrial disorders (MtDs), fatty acid oxidation disorders (FAOD), other IEMs on current newborn screening panels, congenital cardiac great vessel anomalies, renal tubular acidosis, and non-IEMs. The utility of specific AA ratio combinations as biomarkers were evaluated using receiver operating characteristic curves, correlation analysis, principal component analysis, and cutoff SN, SP, and positive predictive value determined from 201 subjects with broad age range. RESULTS: Alanine/Lysine (Ala/Lys) and Ala/Leu as well as (Ala + Pro)/(Leu + Lys) and Ala/Leu ratio combinations effectively discriminated subjects with PDCD from those with other MtDs and IEMs on current newborn screening panels. Specific AA ratio combinations were significantly more sensitive in identifying PDCD than Ala alone or combinations of Ala and/or Pro in the evaluated cohort of subjects. Ala/Lys ≥3.0 and Ala/Leu ≥5.0 as well as (Ala + Pro)/(Leu + Lys) ≥2.5 and Ala/Leu ≥5.0 combination cutoffs identified patients with PDCD with 100% SN and ~85% SP. CONCLUSIONS: With the best predictor of survival and positive cognitive outcome in PDCD being age of diagnosis, PDCD patients would benefit from use of such highly SN and SP AA ratio combination cutoffs as biomarkers for early identification of at-risk newborns, infants, and children, for early intervention(s) with known and/or novel therapeutics for this disorder.

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.

[A case of epilepsy, movement disorders associated with a mutation in the PDHA1 gene in a preschool child]. / Klinicheskii sluchai epilepsii, dvigatel'nykh narushenii, assotsiirovannykh s mutatsiei v gene PDHA1, u rebenka doshkol'nogo vozrasta.

Deficiency of the pyruvate dehydrogenase complex E1-alpha subunit is a rare genetic disease with X-linked dominant inheritance. The clinical spectrum of the disease is extremely wide: from lethal forms in children of the first year of life with lactic acidosis to chronic neurological manifestations with structural changes in the central nervous system without increasing the level of lactate in the blood. The authors report a case of this disease in a preschool child and present the results of laboratory and instrumental studies. The importance of early diagnosis of the disease is emphasized.

Comparison Between Dichloroacetate and Phenylbutyrate Treatment for Pyruvate Dehydrogenase Deficiency.

Pyruvate dehydrogenase (PDH) deficiency is caused by a number of pathogenic variants and the most common are found in the PDHA1 gene. The PDHA1 gene encodes one of the subunits of the PDH enzyme found in a carbohydrate metabolism pathway involved in energy production. Pathogenic variants of PDHA1 gene usually impact the α-subunit of PDH causing energy reduction. It potentially leads to increased mortality in sufferers. Potential treatments for this disease include dichloroacetate and phenylbutyrate, previously used for other diseases such as cancer and maple syrup urine disease. However, not much is known about their efficacy in treating PDH deficiency. Effective treatment for PDH deficiency is crucial as carbohydrate is needed in a healthy diet and rice is the staple food for a large portion of the Asian population. This review analysed the efficacy of dichloroacetate and phenylbutyrate as potential treatments for PDH deficiency caused by PDHA1 pathogenic variants. Based on the findings of this review, dichloroacetate will have an effect on most PDHA1 pathogenic variant and can act as a temporary treatment to reduce the lactic acidosis, a common symptom of PDH deficiency. Phenylbutyrate can only be used on patients with certain pathogenic variants (p.P221L, p.R234G, p.G249R, p.R349C, p.R349H) on the PDH protein. It is hoped that the review would provide an insight into these treatments and improve the quality of lives for patients with PDH deficiency.

Pyruvate dehydrogenase deficiency disease detected by the enzyme activity of peripheral leukocytes.

BACKGROUND: Pyruvate dehydrogenase complex (PDHC) deficiency is a common neurodegenerative disease associated with abnormal mitochondrial energy metabolism. The diagnosis of PDHC is difficult because of the lack of a rapid, accurate, and cost-effective clinical diagnostic method. METHODS: A 4-year-old boy was preliminarily diagnosed with putative Leigh syndrome based on the clinical presentation. PDHC activity in peripheral blood leukocytes and a corresponding gene analysis were subsequently undertaken. Sodium pyruvate 1-13 C was used for the analysis of PDHC activity in peripheral leukocytes. The genes encoding PDHC were then scanned for mutations. RESULTS: The results showed that the corresponding PDHC activity was dramatically decreased to 10.5 nmol/h/mg protein as compared with that of healthy controls (124.6 ± 7.1 nmol/h/mg). The ratio of PDHC to citrate synthase was 2.1% (control: 425.3 ± 27.1). The mutation analysis led to the identification of a missense mutation, NM_000284.4:g214C>T, in exon 3 of PDHC. CONCLUSION: The peripheral blood leukocyte PDHC activity assay may provide a practical enzymatic diagnostic method for PDHC-related mitochondrial diseases.

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.

Pyruvate dehydrogenase deficiency. / Pyruvatdehydrogenase-mangel.

Pyruvate dehydrogenase deficiency is a rare mitochondrial disease leading to energy deficiency in the cells. This particularly affects the central nervous system, resulting in a broad range of neurological symptoms.

[Analysis of a female neonate with pyruvate dehydrogenase complex deficiency].

OBJECTIVE: To analyze the clinical features and genetic basis of a female neonate with muscle weakness, abnormal brain magnetic resonance imaging and elevated blood lactate. METHODS: The patient was subjected to clinical and laboratory examination. Next generation sequencing was carried out for the patient and her relatives. RESULTS: The proband was diagnosed as small for gestational age, with clinical features including muscle weakness, abnormal brain magnetic resonance imaging, increased blood lactate, and acidosis. By genetic testing, a de novo PDHA1 mutation c.1133G to A (p.R378H) was identified, which was known to be pathogenic. The patient was diagnosed with pyruvate dehydrogenase complex deficiency disease (PDCDD), for which vitamin B1, coenzyme Q10, and L-carnitine were prescribed, and a ketogenic diet was recommended. Follow-up at 4-month-7-day found that her blood lactic acid was reduced to normal but her muscle tone was still low. CONCLUSION: The proband was diagnosed as PDCDD caused by a PDHA1 missense mutation. NGS has provided a powerful tool for the diagnosis of such diseases.

LIPT1 deficiency presenting as early infantile epileptic encephalopathy, Leigh disease, and secondary pyruvate dehydrogenase complex deficiency.

Lipoic acid is an essential cofactor for the mitochondrial 2-ketoacid dehydrogenase complexes and the glycine cleavage system. Lipoyltransferase 1 catalyzes the covalent attachment of lipoate to these enzyme systems. Pathogenic variants in LIPT1 gene have recently been described in four patients from three families, commonly presenting with severe lactic acidosis resulting in neonatal death and/or poor neurocognitive outcomes. We report a 2-month-old male with severe lactic acidosis, refractory status epilepticus, and brain imaging suggestive of Leigh disease. Exome sequencing implicated compound heterozygous LIPT1 pathogenic variants. We describe the fifth case of LIPT1 deficiency, whose phenotype progressed to that of an early infantile epileptic encephalopathy, which is novel compared to previously described patients whom we will review. Due to the significant biochemical and phenotypic overlap that LIPT1 deficiency and mitochondrial energy cofactor disorders have with pyruvate dehydrogenase deficiency and/or nonketotic hyperglycinemia, they are and have been presumptively under-diagnosed without exome sequencing.

Enzymatic testing sensitivity, variability and practical diagnostic algorithm for pyruvate dehydrogenase complex (PDC) deficiency.

Pyruvate dehydrogenase complex (PDC) deficiency is a major cause of primary lactic acidemia in children. Prompt and correct diagnosis of PDC deficiency and differentiating between specific vs generalized, or secondary deficiencies has important implications for clinical management and therapeutic interventions. Both genetic and enzymatic testing approaches are being used in the diagnosis of PDC deficiency. However, the diagnostic efficacy of such testing approaches for individuals affected with PDC deficiency has not been systematically investigated in this disorder. We sought to evaluate the diagnostic sensitivity and variability of the various PDC enzyme assays in females and males at the Center for Inherited Disorders of Energy Metabolism (CIDEM). CIDEM data were filtered by lactic acidosis and functional PDC deficiency in at least one cell/tissue type (blood lymphocytes, cultured fibroblasts or skeletal muscle) identifying 186 subjects (51% male and 49% female), about half were genetically resolved with 78% of those determined to have a pathogenic PDHA1 mutation. Assaying PDC in cultured fibroblasts in cases where the underlying genetic etiology is PDHA1, was highly sensitive irrespective of gender; 97% (95% confidence interval [CI]: 90%-100%) and 91% (95% CI: 82%-100%) in females and males, respectively. In contrast to the fibroblast-based testing, the lymphocyte- and muscle-based testing were not sensitive (36% [95% CI: 11%-61%, p=0.0003] and 58% [95% CI: 30%-86%, p=0.014], respectively) for identifying known PDC deficient females with pathogenic PDHA1 mutations. In males with a known PDHA1 mutation, the sensitivity of the various cell/tissue assays (75% lymphocyte, 91% fibroblast and 88% muscle) were not statistically different, and the discordance frequency due to the specific cell/tissue used for assaying PDC was 0.15±0.11. Based on this data, a practical diagnostic algorithm is proposed accounting for current molecular approaches, enzyme testing sensitivity, and variability due to gender, cell/tissue type used for testing, and successive repeat testing.

Pyruvate dehydrogenase deficiency presenting as isolated paroxysmal exercise induced dystonia successfully reversed with thiamine supplementation. Case report and mini-review.

BACKGROUND: Pyruvate dehydrogenase (PDH) deficiency is a disorder of energy metabolism with variable clinical presentations, ranging from severe infantile lactic acidosis to milder chronic neurological disorders. The spectrum of clinical manifestations is continuously expanding. METHODS AND RESULTS: We report on a 19-year-old intelligent female with PDH deficiency caused by a Leu216Ser mutation in PDHA1. She presented with recurrent hemidystonic attacks, triggered by prolonged walking or running, as the unique clinical manifestation that manifested since childhood. Laboratory workup and neuroimages were initially normal but bilateral globus pallidum involvement appeared later on brain MRI. Dystonia completely remitted after high doses of thiamine, remaining free of symptoms after 3 years of follow up. We reviewed the literature for similar observations. CONCLUSIONS: Dystonia precipitated by exercise may be the only symptom of a PDH deficiency, and the hallmark of the disease as high serum lactate or bilateral striatal necrosis at neuroimaging may be absent. A high index of suspicion and follow up is necessary for diagnosis. The clinical presentation of this patient meets the criteria for a Paroxysmal Exercise induced Dystonia, leading us to add this entity as another potential etiology for this type of paroxysmal dyskinesia, which is besides a treatable condition that responds to thiamine supplementation.

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.

[Clinical features of pyruvate dehydrogenase complex deficiency and gene testing in one case].

OBJECTIVE: To analyze the clinical characteristics and genetype of one children who had been diagnosed with pyruvate dehydrogenase complex deficiency. METHOD: Comprehensive analyses of this case were performed, including clinical symptoms, signs, biochemical examinations and therapeutic effects. The eleven exons and splicing areas of PDHA1 were amplified with genomic DNA from whole blood. And variations were investigated by sequencing the PCR product. The patient was diagnosed with pyruvate dehydrogenase complex deficiency by sequence analysis of PDHA1 gene. RESULT: The patient was a 2 years and 4 monthes old boy. He presented with muscle hypotonia and weakness for one year, and experienced recurrent episodes of unstable head control, unable to sit by himself or stand without support, with persistently hyperlactacidemia. Metabolic testing revealed blood lactate 5.37 mmol/L, pyruvate 0.44 mmol/L, and lactate/pyruvate ratio was 12.23. MRI of the brain showed hyperintense signals on the T2 and T2 Flair weighted images in the basal ganglia bilaterally. Sequence analysis of PDHA1 gene showed a G>A point mutation at nucleotide 778, resulting in a substitution of glutarnine for arginine at position 263 (R263Q). And the diagnosis of pyruvate dehydrogenase complex deficiency was identified. By giving the therapy with ketogenic diet, vitamin B(1), coenzyme Q(10) and L-carnitine , the boy was in a stable condition. CONCLUSION: The severity and the clinical phenotypes of pyruvate dehydrogenase complex deficiency varied. Sequence analysis of PDHA1 gene revealed a 788G>A (R263Q) mutation. Patients who presented with unexplained muscle hypotonia, weakness and hyperlactacidemia could be diveded by gene analysis. And appropriate treatment can improve the quality of life.

Mild phenotype in a male with pyruvate dehydrogenase complex deficiency associated with novel hemizygous in-frame duplication of the E1α subunit gene (PDHA1).

Pyruvate dehydrogenase complex (PDHC) deficiency is an inborn error of metabolism that occurs most commonly due to mutations in the X-linked E1α subunit gene (PDHA1). We report a novel duplication of PDHA1 associated with a mild phenotype in a 15-year-old boy who was diagnosed with PDHC deficiency at 4 years of age following a history of seizures and lactic acidosis. The novel c.1087_1119 mutation in exon 11 resulted in an in-frame duplication of 11 amino acids. Measurements of PDHC activity in cultured skin fibroblasts were low, corresponding to 18.6 and 11.6% of the mean with respect to prior controls, whereas the E1 PDH component was absent. He has borderline intellectual functioning and maintains normal lactate levels on a ketogenic diet in between relapses due to illness. Review of the literature reveals wide variation of clinical phenotype in patients with mutations of the E1α subunit gene (PDHA1). There appears to be a higher incidence of normal or borderline intellectual ability in individuals who have insertions or deletions that are in-frame versus those that are out-of-frame. Furthermore, there is no correlation between mean residual PDH activity and phenotype in these patients.

Clinical neurogenetics: neurologic presentations of metabolic disorders.

This article reviews aspects of the neurologic presentations of selected treatable inborn errors of metabolism within the category of small molecule disorders caused by defects in pathways of intermediary metabolism. Disorders that are particularly likely to be seen by neurologists include those associated with defects in amino acid metabolism (organic acidemias, aminoacidopathies, urea cycle defects). Other disorders of small molecule metabolism are discussed as additional examples in which early treatments have the potential for better outcomes.