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Mol Genet Metab Rep. 2014 Nov 28;2:25-31. doi: 10.1016/j.ymgmr.2014.11.001. eCollection 2015 Mar.

Pyruvate carboxylase deficiency: An underestimated cause of lactic acidosis.

Author information

1
Centre de Référence des Maladies Héréditaires du Métabolisme, Hôpital Necker, APHP, Paris, France.
2
INSERM U1124, Université Paris Descartes, Paris, France.
3
Service de Biochimie Métabolomique et Protéomique, Hôpital Necker, APHP, Paris, France.
4
Université Paris Descartes, Paris, France.
5
Département de Génétique, Hôpital Necker, APHP, Paris, France.
6
INSERM U781, Paris, France.
7
IHU Imagine, UMR1163, France.
8
Service de Radiologie Pédiatrique, Hôpital Necker, APHP, Paris, France.
9
INSERM U902, Université d'Evry Val d'Essonne, INSERM UBIAE U902, Boulevard François Miterrand, 91025 Evry, France.

Abstract

Pyruvate carboxylase (PC) is a biotin-containing mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate, thereby being involved in gluconeogenesis and in energy production through replenishment of the tricarboxylic acid (TCA) cycle with oxaloacetate. PC deficiency is a very rare metabolic disorder. We report on a new patient affected by the moderate form (the American type A). Diagnosis was nearly fortuitous, resulting from the revision of an initial diagnosis of mitochondrial complex IV (C IV) defect. The patient presented with severe lactic acidosis and pronounced ketonuria, associated with lethargy at age 23 months. Intellectual disability was noted at this time. Amino acids in plasma and organic acids in urine did not show patterns of interest for the diagnostic work-up. In skin fibroblasts PC showed no detectable activity whereas biotinidase activity was normal. We had previously reported another patient with the severe form of PC deficiency and we show that she also had secondary C IV deficiency in fibroblasts. Different anaplerotic treatments in vivo and in vitro were tested using fibroblasts of both patients with 2 different types of PC deficiency, type A (patient 1) and type B (patient 2). Neither clinical nor biological effects in vivo and in vitro were observed using citrate, aspartate, oxoglutarate and bezafibrate. In conclusion, this case report suggests that the moderate form of PC deficiency may be underdiagnosed and illustrates the challenges raised by energetic disorders in terms of diagnostic work-up and therapeutical strategy even in a moderate form.

KEYWORDS:

Bezafibrate; Lactic acidosis; PC deficiency; Secondary mitochondrial respiratory chain defects

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