ß 2008 Wiley-Liss, Inc.
American Journal of Medical Genetics Part A 146A:1676 – 1681 (2008)
Peroxisomal acyl-CoA-Oxidase Deficiency: Two New Cases Rosalba Carrozzo,1 Carlo Bellini,2 Simona Lucioli,2 Federica Deodato,3 Denise Cassandrini,2 Michela Cassanello,2 Ubaldo Caruso,2 Cristiano Rizzo,3 Teresa Rizza,1 Matteo L. Napolitano,4 Ronald J.A. Wanders,5* Cornelis Jakobs,6 Claudio Bruno,2 Filippo M. Santorelli,1 Carlo Dionisi-Vici,3 and Eugenio Bonioli2* 1
Unit of Molecular Medicine, Bambino Gesu` Children’s Hospital, Rome, Italy Department of Pediatrics, University of Genoa, G. Gaslini Institute, Genoa, Italy 3 Division of Metabolism, Bambino Gesu` Children’s Hospital, Rome, Italy 4 Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy 5 Laboratory Genetic Metabolic Diseases, University Hospital Amsterdam AMC, Amsterdam, The Netherlands 6 Metabolic Unit, VU University Medical Center, Amsterdam, The Netherlands 2
Received 31 August 2007; Accepted 2 January 2008
We report on two new patients with straight-chain acylcoenzyme A oxidase deficiency. Early onset hypotonia, seizures and psychomotor delay were observed in both cases. Plasma very-long-chain fatty acids were abnormal in both patients, whereas the plasma levels of phytanic acid, pristanic acid, the bile acid intermediates DHCA and THCA, and erythrocyte plasmalogen levels were normal. Studies in fibroblasts from the two patients revealed a deficiency of one of the two peroxisomal acyl-CoA oxidases, that is, straightchain acyl-CoA oxidase (ACOX1). Subsequent molecular
analysis of ACOX1 showed a homozygous deletion, which removes a large part of intron 3 and exons 4–14 in the first patient. Mutation analysis in the second patient revealed compound heterozygosity for two mutations, including: (1) a c.692 G > T (p.G231V) mutation and (2) skipping of exon 13 (c.1729_1935del (p.G577_E645del). ß 2008 Wiley-Liss, Inc.
Key words: peroxisomes; acyl-CoA oxidase deficiency; b-oxidation; fatty acids
How to cite this article: Carrozzo R, Bellini C, Lucioli S, Deodato F, Cassandrini D, Cassanello M, Caruso U, Rizzo C, Rizza T, Napolitano ML, Wanders RJA, Jakobs C, Bruno C, Santorelli FM, Dionisi-Vici C, Bonioli E. 2008. Peroxisomal acyl-CoA-oxidase deficiency: Two new cases. Am J Med Genet Part A 146A:1676–1681.
INTRODUCTION
One of the main functions of peroxisomes in human beings is the beta-oxidation of different fatty acids, including very-long-chain fatty acids, pristanic acid, and di- and trihydroxycholestanoic acid. In order to beta-oxidize the different fatty acids, peroxisomes are equipped with two acyl-CoA oxidases, a bifunctional enzyme catalyzing the second and third step of peroxisomal beta-oxidation, and two 3oxoacyl-CoA thiolases [Wanders, 2004b]. The two acyl-CoA oxidases serve different purposes with acylCoA oxidase-1 (ACOX1) being involved in the oxidation of very-long-chain fatty acids, including C26:0, whereas the other acyl-CoA oxidase (ACOX2) is specific for branched-chain fatty acid substrates, including the CoA-esters of pristanic acid as well as di- and trihydroxycholestanoic acid. ACOX1 deficiency [OMIM: #264470] is an autosomal recessive disorder that was first described by Poll-The et al. [1988] who reported two siblings with neonatal hypotonia, seizures, severely delayed
psychomotor development, and neurological deterioration. Brain imaging showed progressive white matter demyelination. Biochemically, patients with ACOX1 deficiency show elevated plasma VLCFA levels, whereas they have normal circulating levels of phytanic, pristanic acid, and di- and trihydroxycholestanoic acid. On the other hand, in patients affected by D-bifunctional protein deficiency phytanic acid, pristanic acid, and di- and trihydroxycholestanoic acid are usually also elevated [Ferdinandusse et al., 2006a], which is explained by the fact that
Rosalba Carrozzo and Carlo Bellini contributed equally to this work. Grant sponsor: Italian Ministry of Health (Ricerca Corrente e Finalizzata). *Correspondence to: Prof. Dr. Ronald J.A. Wanders, Head Lab Genetic Metabolic Diseases, Room F0-224, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. E-mail:
[email protected] and/or Prof. Dr. Eugenio Bonioli, E-mail:
[email protected] DOI 10.1002/ajmg.a.32298
American Journal of Medical Genetics Part A PEROXISOMAL acyl-CoA-OXIDASE DEFICIENCY
D-bifunctional protein is involved in the oxidation of all fatty acids beta-oxidized in peroxisomes [Wanders, 2004b]. In SCPx deficiency, which is the third peroxisomal beta-oxidation deficiency so far identified, very-long-chain fatty acids levels are normal, but pristanic acid and di- and trihydroxycholestanoic acid are elevated [Ferdinandusse et al., 2006b]. ACOX1 deficiency has so far been identified in relatively few patients, that is, 22 patients world wide [Poll-The et al., 1988; Wanders et al., 1990; Suzuki et al., 1994, 2002; Watkins et al., 1995; Kurian et al., 2004; Ferdinandusse et al., 2007]. More importantly, most of these patients have only been described in a cumulative form [Ferdinandusse et al., 2007] and only few patients have been described with full clinical details. In this article we report the clinical, biochemical, and molecular characterization of two acyl-CoA oxidase-1 deficient patients and discuss the pre- and postnatal diagnosis of acyl-CoA oxidase-1 deficiency. PATIENTS AND METHODS Clinical Reports
Patient 1 was born to healthy, related (first cousin) parents from Italian ancestry. Two previous pregnancies resulted in miscarriages. The propositus was delivered by cesarean section at the 33rd week of
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gestation. At birth, the APGAR score was low (6 and 6, at 1 and 5 min, respectively), weight was 2,000 g, and the child showed severe, generalized hypotonia. Generalized epileptic seizures started at 1 month of age. Despite early response to valproate and phenobarbital, tonic–clonic seizures and myoclonic jerks recurred at 6 months, with only temporary remissions. He was severely delayed, and did not achieve postural control. At 4 years of age spastic tetraplegia and severe mental retardation with a poor response to visual and auditory stimuli were evident. EEG showed a disorganized pattern with slow waves in the occipital recordings. Language development was virtually absent. A brain CT scan showed moderate cortical atrophy. In the following months, he progressively worsened and displayed dysphagia, frequent lower respiratory tract infections, apneic and epileptic seizures, and repeated episodes of cardiorespiratory arrest. Brain MRI at 5.2 years showed brain atrophy, severe white matter abnormalities and peripheral contrast enhancement, hyperintensty of corticopontine tracts, and thinning of the corpus callosum (Fig. 1A–C). Fundoscopy showed bilateral optic atrophy. Brainstem auditory evoked responses revealed a mild sensorineural hearing defect. Serum transaminases were increased (AST: 243 U/L, ALT: 405 U/L, normal T missense mutation in exon 6 (arrow), changing an encoded Glycine to Valine, and of the cDNA indicating the skipping of exon 13. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]
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DISCUSSION
The group of peroxisomal disorders is clinically and genetically heterogeneous and is generally classified into two main categories, that is, the peroxisome biogenesis disorders (PBDs) and the single peroxisomal enzyme defects [Depreter et al., 2003; Weller et al., 2003; Wanders, 2004a; Steinberg et al., 2006]. The PBD group contains two subgroups, which include: (1) the Zellweger spectrum disorders with a full defect in peroxisome biogenesis and (2) rhizomelic chondrodysplasia punctata type 1, in which there is only a partial defect in peroxisome biogenesis [Wanders, 2004a]. The Zellweger spectrum disorders include Zellweger syndrome and its phenotypic variants, that is, infantile Refsum disease, and neonatal adrenoleukodystrophy. The group of single peroxisomal enzyme defects can be subdivided into four subgroups, including: (1) the disorders of peroxisomal beta-oxidation; (2) the disorders of etherphospholipid biosynthesis; (3) the disorders of fatty acid alpha-oxidation, and (4) the disorders of glyoxylate metabolism. Among the disorders of peroxisomal beta-oxidation, X-linked adrenoleukodystrophy is most frequent, followed by D-bifunctional protein deficiency, acyl-CoA oxidase1 deficiency, 2-methylacyl-CoA racemase deficiency and SCPx deficiency [Wanders and Waterham, 2006]. Precise diagnosis of peroxisomal disorders requires a complex biochemical and genetic approach due to the marked heterogeneity in the phenotypic expression of patients. Indeed, there are marked clinical similarities between patients, either affected by a peroxisome biogenesis disorder or a single enzymatic defect, which makes it impossible to discriminate between the disorders of peroxisome biogenesis and certain single enzyme deficiencies, notably D-bifunctional protein deficiency and acyl-CoA oxidase deficiency on clinical grounds. In this study, we present two patients with clinical findings suggestive of a peroxisomal disorder. Determination of plasma VLCFA as well as pristanic, phytanic and di- and trihydroxycholestanoic acid and erythrocyte plasmalogens along with direct biochemical analyses and gene testing confirmed ACOX1 deficiency. In this case the profile of peroxisomal abnormalities as detected in plasma from the two patients was very suggestive for acyl-
CoA oxidase deficiency. Indeed, as summarized in Table II different profiles are found in the other peroxisomal disorders in which very-long-chain fatty acids are abnormal with the exception of X-linked adrenoleukodystrophy in which a similar profile of peroxisomal metabolites, as observed in acyl-CoA oxidase deficiency, is found. However, X-linked adrenoleukodystrophy could easily be ruled out, based on the clinical signs and symptoms of the two patients (compare Table I). A number of indications suggests that the mutations found in the two patients are definitely pathogenic. The homozygous 15.5 kb deletion found in Patient 1 predictably results in a loss-of-function of the enzyme, which was corroborated by immunoblot data. The heterozygous p.G231V mutation we detected in Patient 2 affects a residue that is highly conserved during evolution. The mutation is believed to alter protein conformation and is absent in over 200 ethnically matched control chromosomes. The exon 13 deletion (amino acids p.G577p.E645) removes the terminal part of a functionally relevant protein domain (Acyl_CoA_ox_C domain, PF01756, www.ensembl.org) involved in the peroxisomal oxidation of VLCFA. As reported in Table I, the clinical presentation of our patients, like the presentation of the previously described cases, shows a fairly homogeneous pattern that somehow is different from the Zellweger spectrum disorders. Patients present with neonatal hypotonia, early-onset seizures, psychomotor retardation, sensory deafness and various degrees of optic atrophy/retinal degeneration. However, in most cases clinical reports show that they acquired some gross motor skills during the first 2 years of life (including walking). Furthermore, progressive neurological regression and the appearance of pyramidal signs became evident. Unlike all other reported ACOX1 cases, our first patient achieved no postural control or motor ability throughout his whole life. The typical MRI finding of ACOX-1 deficiency is diffuse leukodystrophy with progressive demyelination and characteristic bilateral contrast enhancement lesions in the centrum semiovale. On the other hand, our second patient showed polymicrogyria that represents a frequent finding in Zellweger spectrum disorders [Barth et al., 2004] and D-bifunctional protein deficiency [Watkins et al., 1995].
TABLE II. Peroxisomal Metabolite Profiles in Acyl-CoA Oxidase-1 Deficiency and the Other Peroxisomal Disorders
Very-long-chain fatty acids Pristanic acid Phytanic acid Di- and trihydroxycholestanoic acid Erythrocyte plasmalogens a
ZSDs
ACOX1 deficiency
X-ALD
DBP deficiency
SCPx deficiency
AMACR deficiency
" n-" n-" " n-#
" N N N N
" N N N N
" n-" n-" "a N
N n-" n-" "a N
N " n-" " N
May be minimally abnormal to even normal in exceptional cases.
American Journal of Medical Genetics Part A PEROXISOMAL acyl-CoA-OXIDASE DEFICIENCY
In conclusion, the description of two additional ACOX1 deficient patients, adds new insight into the clinical, neuroradiological and molecular aspects of this disorder that represents one of the rarer inherited defects of peroxisome function. ACKNOWLEDGMENTS
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