A family with pyruvate dehydrogenase complex deficiency due to a novel C>T substitution at nucleotide position 407 in exon 4 of the X-linked Epsilon1alpha gene

Manifestations of X-linked pyruvate dehydrogenase complex deficiency in female PDHA1 carriers

BACKGROUND AND PURPOSE

Pyruvate dehydrogenase complex deficiency is in up to 90% caused by pathogenic variants in the X-linked PDHA1 gene. We aimed to investigate female relatives of index patients with PDHA1-related disease to (i) describe the prevalence of female PDHA1 carriers, (ii) determine whether they had symptoms and signs, and (iii) delineate the associated phenotype.

METHODS

In a national population-based study, we identified 37 patients with pathogenic variants in PDHA1. Sanger sequencing for the presence of the pathogenic variant was performed in their mothers and female relatives. The identified female carriers were clinically assessed, and their medical records were reviewed.

RESULTS

The proportion carrying a de novo variant was 86%. We identified seven female PDHA1 carriers from five families. Five of them exhibited clinical features of the disease and were previously undiagnosed; all had signs of peripheral axonal neuropathy, four presented with strokelike episodes including two with Leigh-like lesions, and three had facial stigmata.

CONCLUSIONS

PDHA1-related disease is underrecognized in heterozygous female carriers. Peripheral axonal neuropathy, strokelike and Leigh-like changes, and facial dysmorphism should raise suspicion of the disorder. Genetic analysis and clinical examination of potential female carriers are important for genetic counseling and have implications for treatment.

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.

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.

Phenotypic and genotypic variability in Alpers syndrome

BACKGROUND

Alpers syndrome is one of the most common phenotypes of mitochondrial disorders in early childhood and has been associated with pathogenic mutations in POLG1.

AIMS

To investigate the phenotypic-genotypic correlations in Alpers syndrome and to identify potential differences among patients with Alpers syndrome with or without pathogenic POLG1 mutations.

METHODS

Patients with the phenotype of Alpers syndrome who were referred to our pediatric hospital during 1984-2007 and were diagnosed with mitochondrial encephalomyopathy underwent further biochemical, morphological and genetic investigations.

RESULTS

A total of 19 patients were included in the study, of whom six had pathogenic POLG1 mutations including a novel mutation (c.907 G>A, p.Gly303Arg). Complete mtDNA sequencing in the subgroup without POLG1 mutations showed 5 novel and 5 very rare mtDNA variants considered as rare polymorphisms. Compared to POLG1(-) patients, the POLG1(+) patients more frequently had seizures at onset, which often became refractory. Ataxia and stroke-like episodes were much more common, while microcephaly and spasticity were encountered almost solely in the POLG1(-) group. Hepatic and ophthalmological involvement developed in 79% and 88% of patients, respectively. Most of the patients in both groups had predominant deficiency of complex I. In addition to the major degenerative changes in the cerebral cortex, the basal ganglia, thalamus and white matter were also involved to variable extent.

CONCLUSION

Alpers syndrome is a heterogeneous syndrome that should be considered in patients with early-onset progressive cortical encephalopathy regardless of liver involvement. The phenotype is different depending on the presence or absence of POLG1 mutations.

The spectrum of pyruvate dehydrogenase complex deficiency: clinical, biochemical and genetic features in 371 patients

CONTEXT

Pyruvate dehydrogenase complex (PDC) deficiency is a genetic mitochondrial disorder commonly associated with lactic acidosis, progressive neurological and neuromuscular degeneration and, usually, death during childhood. There has been no recent comprehensive analysis of the natural history and clinical course of this disease.

OBJECTIVE

We reviewed 371 cases of PDC deficiency, published between 1970 and 2010, that involved defects in subunits E1α and E1β and components E1, E2, E3 and the E3 binding protein of the complex.

DATA SOURCES AND EXTRACTION

English language peer-reviewed publications were identified, primarily by using PubMed and Google Scholar search engines.

RESULTS

Neurodevelopmental delay and hypotonia were the commonest clinical signs of PDC deficiency. Structural brain abnormalities frequently included ventriculomegaly, dysgenesis of the corpus callosum and neuroimaging findings typical of Leigh syndrome. Neither gender nor any clinical or neuroimaging feature differentiated the various biochemical etiologies of the disease. Patients who died were younger, presented clinically earlier and had higher blood lactate levels and lower residual enzyme activities than subjects who were still alive at the time of reporting. Survival bore no relationship to the underlying biochemical or genetic abnormality or to gender.

CONCLUSIONS

Although the clinical spectrum of PDC deficiency is broad, the dominant clinical phenotype includes presentation during the first year of life; neurological and neuromuscular degeneration; structural lesions revealed by neuroimaging; lactic acidosis and a blood lactate:pyruvate ratio ≤ 20.

The spectrum of pyruvate dehydrogenase complex deficiency: clinical, biochemical and genetic features in 371 patients

CONTEXT

Pyruvate dehydrogenase complex (PDC) deficiency is a genetic mitochondrial disorder commonly associated with lactic acidosis, progressive neurological and neuromuscular degeneration and, usually, death during childhood. There has been no recent comprehensive analysis of the natural history and clinical course of this disease.

OBJECTIVE

We reviewed 371 cases of PDC deficiency, published between 1970 and 2010, that involved defects in subunits E1α and E1β and components E1, E2, E3 and the E3 binding protein of the complex.

DATA SOURCES AND EXTRACTION

English language peer-reviewed publications were identified, primarily by using PubMed and Google Scholar search engines.

RESULTS

Neurodevelopmental delay and hypotonia were the commonest clinical signs of PDC deficiency. Structural brain abnormalities frequently included ventriculomegaly, dysgenesis of the corpus callosum and neuroimaging findings typical of Leigh syndrome. Neither gender nor any clinical or neuroimaging feature differentiated the various biochemical etiologies of the disease. Patients who died were younger, presented clinically earlier and had higher blood lactate levels and lower residual enzyme activities than subjects who were still alive at the time of reporting. Survival bore no relationship to the underlying biochemical or genetic abnormality or to gender.

CONCLUSIONS

Although the clinical spectrum of PDC deficiency is broad, the dominant clinical phenotype includes presentation during the first year of life; neurological and neuromuscular degeneration; structural lesions revealed by neuroimaging; lactic acidosis and a blood lactate:pyruvate ratio ≤20.

MRI features of 4 female patients with pyruvate dehydrogenase E1 alpha deficiency

Pyruvate dehydrogenase complex is a key intramitochondrial multienzyme complex required for the conversion of pyruvate to acetyl-CoA. Most patients with pyruvate dehydrogenase deficiency have a defect in the E1 alpha subunit, associated with mutations in the PDHA1 gene. In this report, we submit detailed magnetic resonance images in 4 affected female patients with PDHA1 mutations who had with severe cortical atrophy, dilated ventricles, and an incomplete corpus callosum. In one of these patients, the magnetic resonance imaging pattern prompted molecular diagnostic testing when enzymatic testing was normal. We underscore that this constellation of features, which may be misdiagnosed as periventricular leukomalacia, illustrates a pattern highly suggestive of a deficiency of pyruvate dehydrogenase E1 alpha in female patients and should trigger appropriate diagnostic investigations.

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.

Intermittent peripheral weakness as the presenting feature of pyruvate dehydrogenase deficiency

Two unrelated children presenting with episodic isolated peripheral weakness were found to have pyruvate dehydrogenase (PDH) deficiency (OMIM 312170) due to previously undescribed mutations (Pro250Thr, Arg88Cys) in the gene for the E1alpha subunit (PDHA1). Taken in context with the literature, these patients suggest that acute weakness initially resembling Guillain-Barré syndrome is a potentially reversible and probably underdiagnosed manifestation of PDH deficiency and that peripheral nerve function should be evaluated in PDH-deficient patients.

Therapeutic potential of dichloroacetate for pyruvate dehydrogenase complex deficiency

We reviewed the use of oral dichloroacetate (DCA) in the treatment of children with congenital lactic acidosis caused by mutations in the pyruvate dehydrogenase complex (PDC). The case histories of 46 subjects were analyzed with regard to diagnosis, clinical presentation and response to DCA. DCA decreased blood and cerebrospinal fluid lactate concentrations, and was generally well tolerated. DCA may be particularly effective in children with PDC deficiency by stimulating residual enzyme activity and, consequently, cellular energy metabolism. A controlled trial is needed to determine the definitive role of DCA in the management of this devastating disease.