Abstract We report three unrelated probands, two male and one female, diagnosed with Aicardi‐Goutières syndrome (AGS) after screening positive on California newborn screening (CA NBS) for X‐linked adrenoleukodystrophy (X‐ALD) due to elevated C26:0 lysophosphatidylcholine (C26:0‐LPC). Follow‐up evaluation was notable for elevated C26:0, C26:1, and C26:0/C22:0 ratio, and normal red blood cell plasmalogens levels in all three probands. Diagnoses were confirmed by molecular sequencing prior to 12 months of age after clinical evaluation was inconsistent with X‐ALD or suggestive of AGS. For at least one proband, the early diagnosis of AGS enabled candidacy for enrollment into a therapeutic clinical trial. This report demonstrates the importance of including AGS on the differential diagnosis for individuals who screen positive for X‐ALD, particularly infants with abnormal neurological features, as this age of onset would be highly unusual for X‐ALD. While AGS is not included on the Recommended Universal Screening Panel, affected individuals can be identified early through state NBS programs so long as providers are aware of a broader differential that includes AGS. This report is timely, as state NBS algorithms for X‐ALD are actively being established, implemented, and refined.
Carnitine palmitoyltransferase I (CPT I) catalyzes the formation of acylcarnitine, the first step in the oxidation of long-chain fatty acids in mitochondria. The enzyme exists as liver (L-CPT I) and muscle (M-CPT I) isoforms that are encoded by separate genes. Genetic deficiency of L-CPT I, which has been reported in 16 patients from 13 families, is characterized by episodes of hypoketotic hypoglycemia beginning in early child-hood and is usually associated with fasting or illness. To date, only two mutations associated with L-CPT I deficiency have been reported. In the present study we have identified and characterized the mutations underlying L-CPT I deficiency in six patients: five with classic symptoms of L-CPT I deficiency and one with symptoms that have not previously been associated with this disorder (muscle cramps and pain). Transfection of the mutant L-CPT I cDNAs in COS cells resulted in L-CPT I mRNA levels that were comparable to those expressed from the wild-type construct. Western blotting revealed lower levels of each of the mutant proteins, indicating that the low enzyme activity associated with these mutations was due, at least in part, to protein instability. The patient with atypical symptoms had ~20% of normal L-CPT I activity and was homozygous for a mutation (c.1436C→T) that substituted leucine for proline at codon 479. Assays performed with his cultured skin fibroblasts indicated that this mutation confers partial resistance to the inhibitory effects of malonyl-CoA.The demonstration of L-CPT I deficiency in this patient suggests that the spectrum of clinical sequelae associated with loss or alteration of L-CPT I function may be broader than was previously recognized.—Brown, N. F., R. S. Mullur, I. Subramanian, V. Esser, M. J. Bennett, J-M. Saudubray, A. S. Feigenbaum, J. A. Kobari, P. M. Macleod, J. D. McGarry, and J. C. Cohen. Molecular characterization of L-CPT I deficiency in six patients: insights into function of the native enzyme. J. Lipid Res. 2001. 42: 1134–1142.
Heterozygous somatic mutations in the genes encoding isocitrate dehydrogenase-1 and -2 (IDH1 and IDH2) were recently discovered in human neoplastic disorders. These mutations disable the enzymes' normal ability to convert isocitrate to 2-ketoglutarate (2-KG) and confer on the enzymes a new function: the ability to convert 2-KG to d-2-hydroxyglutarate (D-2-HG). We have detected heterozygous germline mutations in IDH2 that alter enzyme residue Arg(140) in 15 unrelated patients with d-2-hydroxyglutaric aciduria (D-2-HGA), a rare neurometabolic disorder characterized by supraphysiological levels of D-2-HG. These findings provide additional impetus for investigating the role of D-2-HG in the pathophysiology of metabolic disease and cancer.
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