ABSTRACT
Pyruvate carboxylase deficiency is a rare metabolic disorder, with three different phenotypes. We aim to report the case of a newborn presenting the severe neonatal form of this deficiency (the B or "French" phenotype, hypokinesia and rigidity being the main features) and the results of the study of classic neurotransmitters involved in movement control. Hyperdopaminergic transmission (both in the cerebrospinal fluid and in the substantia nigra) and hypoGABAergic transmission (in the substantia nigra) were found. Both gamma-aminobutyric acid and dopamine markers were found coexisting in individual neurons of the substantia nigra. This is the first time this phenomenon has been reported in the literature. We discuss the possible role of GABAergic deficiency, its interaction with other neurotransmitters and its implication in neurotransmitter homeostasis. A better comprehension of that field would increase understanding of the pathophysiology of neurological symptoms and neurotransmitter plasticity.
Subject(s)
Parkinsonian Disorders/diagnosis , Pyruvate Carboxylase Deficiency Disease/diagnosis , Brain/metabolism , Brain/pathology , Fatal Outcome , Female , GABAergic Neurons/physiology , Humans , Parkinsonian Disorders/enzymology , Parkinsonian Disorders/physiopathology , Pyruvate Carboxylase Deficiency Disease/physiopathology , Synaptic Transmission , Tyrosine 3-Monooxygenase/metabolismABSTRACT
OBJECTIVE: Pyruvate carboxylase (PC) deficiency is a rare metabolic disease. Recently, therapeutic possibilities have been introduced. We aimed to report the largest series of the B type of PC deficiency, focusing on some neurological aspects that have not yet been documented. METHODS: We retrospectively studied nine patients with the severe neonatal form of PC deficiency diagnosed in our hospital. Detailed clinical features, brain imaging, biochemical characteristics, and global outcome are reported. RESULTS: All patients had axial hypotonia and tachypnea during the first hours of life. The initial level of consciousness was preserved in most patients. Abnormal movements (high-amplitude tremor and hypokinesia) and bizarre ocular behavior were the most common findings, whereas epilepsy was infrequent. Brain magnetic resonance imaging mostly disclosed cystic periventricular leukomalacia. Hypoglycemia, lactic acidosis, and hypercitrullinemia were invariably found. Hyperammoniemia, hypernatremia, and high proline and lysine were frequently detected. A rapid fatal outcome was observed in most patients. INTERPRETATION: Clinical and biochemical characteristics of this deficiency are highly suggestive. Abnormal movements such as rigidity and hypokinesia (hypokinetic-rigid syndrome) are an important hallmark and may orientate to PC deficiency when associated with severe lactic acidosis.
Subject(s)
Nervous System Diseases , Pyruvate Carboxylase Deficiency Disease , Amino Acids/metabolism , Brain/metabolism , Brain/pathology , Female , Humans , Infant , Infant, Newborn , Magnetic Resonance Imaging , Male , Nervous System Diseases/etiology , Nervous System Diseases/physiopathology , Pyruvate Carboxylase Deficiency Disease/complications , Pyruvate Carboxylase Deficiency Disease/physiopathology , Retrospective Studies , Seizures/physiopathologyABSTRACT
Pyruvate carboxylase [EC 6.4.1.1] is a member of the family of biotin-dependent carboxylases and is found widely among eukaryotic tissues and in many prokaryotic species. It catalyses the ATP-dependent carboxylation of pyruvate to form oxaloacetate which may be utilised in the synthesis of glucose, fat, some amino acids or their derivatives and several neurotransmitters. Diabetes and hyperthyroidism increase the level of expression of pyruvate carboxylase in the long term, while its activity in the short term is controlled by the intramitochondrial concentrations of acetyl-CoA and pyruvate. Many details of this enzyme's regulation are yet to be described in molecular terms. However, progress towards this goal and towards understanding the relationship of pyruvate carboxylase structure to its catalytic reaction mechanism, has been enormously enhanced recently by the cloning and sequencing of genes and cDNAs encoding the approximately 130 kDa subunit of this homotetramer. Defects in the expression or biotinylation of pyruvate carboxylase in humans almost invariably results in early death or at best a severely debilitating psychomotor retardation, clearly reflecting the vital role it plays in intermediary metabolism in many tissues including the brain.
