Selective involvement of the globus pallidus and dentate nucleus in succinic semialdehyde dehydrogenase deficiency

MRI findings in a 12-year-old boy with succinic semialdehyde dehydrogenase (SSADH) deficiency are described. SSADH deficiency is a rare neurometabolic disorder of GABA catabolism. The clinical diagnosis is difficult and the disease is underdiagnosed. MRI showed an unusual pattern with hyperintense signal in the globus pallidus and cerebellar dentate nucleus in T2-weighted images. The remaining basal ganglia and white matter were normal. This is the second report showing this particular pattern of pallidal-dentate nucleus involvement, which might be suggestive for SSADH deficiency.

Structure of human succinic semialdehyde dehydrogenase gene: identification of promoter region and alternatively processed isoforms

Mitochondrial NAD(+)-dependent succinic semialdehyde dehydrogenase (ALDH5A1, SSADH) represents the last enzyme in the GABA catabolism and irreversibly oxidizes SSA to succinate. In human, SSADH deficiency results in 4-hydroxybutyric aciduria, an autosomal recessive disorder due to an accumulation of GABA and 4-hydroxybutyric acid in the CNS. We already identified SSADH gene on human chromosome 6p22 and characterized the coding region. Furthermore, we described the first two mutations causing the disease. We report here the complete cDNA and genomic structure of the gene. A single transcription start site was identified by RNase protection 122 bp upstream of the ATG. EST database search and reporter gene constructs of the 3(') genomic region showed that the two major SSADH mRNA isoforms are due to alternative polyadenylation sites. The two mRNAs of 1827 and 5225 nt were analyzed for differential stability and translation efficiency. The analysis of mRNA turnover showed that both SSADH transcripts are equally stable. Similarly, a measurement of polysomal association capability of the two GFP-SSADH reporter mRNAs (containing the 3' UTR regions of the two SSADH mRNAs) did not reveal any difference. However, we cannot exclude the fact that differential properties could be restricted to particular physiological conditions and/or specific tissues. We have also identified an alternatively spliced small exon, which may lead to a novel isoform of the enzyme. Furthermore, we report here on naturally occurring missense variants, which may significantly contribute to inter-individual variation of SSADH activity, possibly influencing GABA and GHB endogenous levels.

Embryonic retinoic acid synthesis is required for forelimb growth and anteroposterior patterning in the mouse

Numerous studies, often performed on avian embryos, have implicated retinoic acid (RA) in the control of limb bud growth and patterning. Here we have investigated whether the lack of endogenous RA synthesis affects limb morphogenesis in mutant mouse embryos deficient for the retinaldehyde dehydrogenase 2 (Raldh2/Aldh1a2). These mutants, which have no detectable embryonic RA except in the developing retina, die at E9.5-E10 without any evidence of limb bud formation, but maternal RA supplementation through oral gavage from E7.5 can extend their survival. Such survivors exhibit highly reduced forelimb rudiments, but apparently normal hindlimbs. By providing RA within maternal food, we found both a stage- and dose-dependency for rescue of forelimb growth and patterning. Following RA supplementation from E7.5 to 8.5, mutant forelimbs are markedly hypoplastic and lack anteroposterior (AP) patterning, with a single medial cartilage and 1-2 digit rudiments. RA provided until E9.5 significantly rescues forelimb growth, but cannot restore normal AP patterning. Increasing the RA dose rescues the hypodactyly, but leads to lack of asymmetry of the digit pattern, with abnormally long first digit or symmetrical polydactyly. Mutant forelimb buds are characterized by lack of expression or abnormal distal distribution of Sonic hedgehog (Shh) transcripts, sometimes with highest expression anteriorly. Downregulation or ectopic anterior expression of Fgf4 is also seen. As a result, genes such as Bmp2 or Hoxd genes are expressed symmetrically along the AP axis of the forelimb buds, and/or later, of the autopod. We suggest that RA signaling cooperates with a posteriorly restricted factor such as dHand, to generate a functional zone of polarizing activity (ZPA).

Why can't Chinese Han drink alcohol? Hepatitis B virus infection and the evolution of acetaldehyde dehydrogenase deficiency

An aldehyde-dehydrogenase (ALDH2) deficiency is a biological curb on excess alcohol-drinking. This enzyme deficiency is very common amongst Oriental people while it is relatively rare for most other populations. We observe that there is good geographical correlation between the prevalence of the mutant ALDH2*2 alleles and hepatitis B virus (HBV) infections. Populations that demonstrate a high ALDH2*2 prevalence are all located in HBV-endemic areas. Further, studies have shown that HBV and alcohol drinking exhibit a synergistic effect upon liver cirrhosis and cancer. A shorter life span for those with HBV infection and heavy alcohol consumption may result in a selection of the ALDH2*2 gene. We postulate that there may be patterns of evolutionary adaptation for ALDH2 deficiency in certain HBV-endemic areas and that these adaptations can produce differences in human alcohol-drinking capability.

Therapeutic intervention in mice deficient for succinate semialdehyde dehydrogenase (gamma-hydroxybutyric aciduria)

Therapeutic intervention for human succinic semialdehyde dehydrogenase (SSADH) deficiency (gamma-hydroxybutyric aciduria) has been limited to vigabatrin (VGB). Pharmacologically, VGB should be highly effective due to 4-aminobutyrate-transaminase (GABA-transaminase) inhibition, lowering succinic semialdehyde and, thereby, gamma-hydroxybutyric acid (GHB) levels. Unfortunately, clinical efficacy has been limited. Because GHB possesses a number of potential receptor interactions, we addressed the hypothesis that antagonism of these interactions in mice with SSADH deficiency could lead to the development of novel treatment strategies for human patients. SSADH-deficient mice have significantly elevated tissue GHB levels, are neurologically impaired, and die within 4 weeks postnatally. In the current report, we compared oral versus intraperitoneal administration of VGB, CGP 35348 [3-aminopropyl(diethoxymethyl)phosphinic acid, a GABA(B) receptor antagonist], and the nonprotein amino acid taurine in rescue of SSADH-deficient mice from early death. In addition, we assessed the efficacy of the specific GHB receptor antagonist NCS-382 (6,7,8,9-tetrahydro-5-[H]benzocycloheptene-5-ol-6-ylideneacetic acid) using i.p. administration. All interventions led to significant lifespan extension (22-61%), with NCS-382 being most effective (50-61% survival). To explore the limited human clinical efficacy of VGB, we measured brain GHB and gamma-aminobutyric acid (GABA) levels in SSADH-deficient mice receiving VGB. Whereas high-dose VGB led to the expected elevation of brain GABA, we found no parallel decrease in GHB levels. Our data indicate that, at a minimum, GHB and GABA(B) receptors are involved in the pathophysiology of SSADH deficiency. We conclude that taurine and NCS-382 may have therapeutic relevance in human SSADH deficiency and that the poor clinical efficacy of VGB in this disease may relate to an inability to decrease brain GHB concentrations.

Genetic evidence that oxidative derivatives of retinoic acid are not involved in retinoid signaling during mouse development

Retinoic acid, the active derivative of vitamin A (retinol), is a hormonal signaling molecule that acts in developing and adult tissues. The Cyp26a1 (cytochrome p450, 26) protein metabolizes retinoic acid into more polar hydroxylated and oxidized derivatives. Whether some of these derivatives are biologically active metabolites has been debated. Cyp26a1(-/-) mouse fetuses have lethal morphogenetic phenotypes mimicking those generated by excess retinoic acid administration, indicating that human CYP26A1 may be essential in controlling retinoic acid levels during development. This hypothesis suggests that the Cyp26a1(-/-) phenotype could be rescued under conditions in which embryonic retinoic acid levels are decreased. We show that Cyp26a1(-/-) mice are phenotypically rescued by heterozygous disruption of Aldh1a2 (also known as Raldh2), which encodes a retinaldehyde dehydrogenase responsible for the synthesis of retinoic acid during early embryonic development. Aldh1a2 haploinsufficiency prevents the appearance of spina bifida and rescues the development of posterior structures (sacral/caudal vertebrae, hindgut, urogenital tract), while partly preventing cervical vertebral transformations and hindbrain pattern alterations in Cyp26a1(-/-) mice. Thus, some of these double-mutant mice can reach adulthood. This study is the first report of a mutation acting as a dominant suppressor of a lethal morphogenetic mutation in mammals. We provide genetic evidence that ALDH1A2 and CYP26A1 activities concurrently establish local embryonic retinoic acid levels that must be finely tuned to allow posterior organ development and to prevent spina bifida.

Excessive vitamin A toxicity in mice genetically deficient in either alcohol dehydrogenase Adh1 or Adh3

Alcohol dehydrogenase (ADH) deficiency results in decreased retinol utilization, but it is unclear what physiological roles the several known ADHs play in retinoid signaling. Here, Adh1, Adh3, and Adh4 null mutant mice have been examined following acute and chronic vitamin A excess. Following an acute dose of retinol (50 mg.kg(-1)), metabolism of retinol to retinoic acid in liver was reduced 10-fold in Adh1 mutants and 3.8-fold in Adh3 mutants, but was not significantly reduced in Adh4 mutants. Acute retinol toxicity, assessed by determination of the LD(50) value, was greatly increased in Adh1 mutants and moderately increased in Adh3 mutants, but only a minor effect was observed in Adh4 mutants. When mice were propagated for one generation on a retinol-supplemented diet containing 10-fold higher vitamin A than normal, Adh3 and Adh4 mutants had essentially the same postnatal survival to adulthood as wild-type (92-95%), but only 36% of Adh1 mutants survived to adulthood with the remainder dying by postnatal day 3. Adh1 mutants surviving to adulthood on the retinol- supplemented diet had elevated serum retinol signifying a clearance defect and elevated aspartate aminotransferase indicative of increased liver damage. These findings indicate that ADH1 functions as the primary enzyme responsible for efficient oxidative clearance of excess retinol, thus providing protection and increased survival during vitamin A toxicity. ADH3 plays a secondary role. Our results also show that retinoic acid is not the toxic moiety during vitamin A excess, as Adh1 mutants have less retinoic acid production while experiencing increased toxicity.

Novel retinoic acid generating activities in the neural tube and heart identified by conditional rescue of Raldh2 null mutant mice

Retinoid control of vertebrate development depends upon tissue-specific metabolism of retinol to retinoic acid (RA). The RA biosynthetic enzyme RALDH2 catalyzes much, but not all, RA production in mouse embryos, as revealed here with Raldh2 null mutants carrying an RA-responsive transgene. Targeted disruption of Raldh2 arrests development at midgestation and eliminates all RA synthesis except that associated with Raldh3 expression in the surface ectoderm of the eye field. Conditional rescue of Raldh2–/– embryos by limited maternal RA administration allows development to proceed and results in the establishment of additional sites of RA synthesis linked to Raldh1 expression in the dorsal retina and to Raldh3 expression in the ventral retina, olfactory pit and urinary tract. Unexpectedly, conditionally rescued Raldh2–/– embryos also possess novel sites of RA synthesis in the neural tube and heart that do not correspond to expression of Raldh1-3. RA synthesis in the mutant neural tube was localized in the spinal cord, posterior hindbrain and portions of the midbrain and forebrain, whereas activity in the mutant heart was localized in the conotruncus and sinus venosa. In the posterior hindbrain, this novel RA-generating activity was expressed during establishment of rhombomeric boundaries. In the spinal cord, the novel activity was localized in the floorplate plus in the intermediate region where retinoid-dependent interneurons develop. These novel RA-generating activities in the neural tube and heart fill gaps in our knowledge of how RA is generated spatiotemporally and may, along with Raldh1 and Raldh3, contribute to rescue of Raldh2–/– embryos by producing RA locally.

Focal neurometabolic alterations in mice deficient for succinate semialdehyde dehydrogenase

Metabolite profiling in succinate semialdehyde dehydrogenase (SSADH; Aldh5a1-/-) deficient mice previously revealed elevated gamma-hydroxybutyrate (GHB) and total GABA in urine and total brain and liver extracts. In this study, we extend our metabolic characterization of these mutant mice by documenting elevated GHB and total GABA in homogenates of mutant kidney, pancreas and heart. We quantified beta-alanine (a GABA homolog and putative neurotransmitter) to address its potential role in pathophysiology. We found normal levels of beta-alanine in urine and total homogenates of mutant brain, heart and pancreas, but elevated concentrations in mutant kidney and liver extracts. Amino acid analysis in mutant total brain homogenates revealed no abnormalities except for significantly decreased glutamine, which was normal in mutant liver and kidney extracts. Regional amino acid analysis (frontal cortex, parietal cortex, hippocampus and cerebellum) in mutant mice confirmed glutamine results. Glutamine synthetase protein and mRNA levels in homogenates of mutant mouse brain were normal. We profiled organic acid patterns in mutant brain homogenates to assess brain oxidative metabolism and found normal concentrations of Kreb's cycle intermediates but increased 4,5-dihydroxyhexanoic acid (a postulated derivative of succinic semialdehyde) levels. We conclude that SSADH-deficient mice represent a valid metabolic model of human SSADH deficiency, manifesting focal neurometabolic abnormalities which could provide key insights into pathophysiologic mechanisms.

Neuroleptic malignant syndrome in a patient with succinic semialdehyde dehydrogenase deficiency

A patient suffering from a rare enzyme deficiency developed a malignant neuroleptic syndrome after having been treated with one single dose of haloperidol. We investigated the patient's serum for all frequent polymorphisms in cytochrome P450 2D6, assuming him to be a poor neuroleptic metabolizer. We will also discuss other potential mechanisms inducing this disturbance and its differential diagnoses.

Clinical, biochemical and molecular genetic characteristics of 19 patients with the Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS) is an autosomal recessively inherited neurocutaneous disorder caused by a deficiency of the microsomal enzyme fatty aldehyde dehydrogenase (FALDH). We report the clinical characteristics and the results of molecular studies in 19 SLS patients. Patients 1-17 show the classical triad of severe clinical abnormalities including ichthyosis, mental retardation and spasticity. Most patients were born preterm, and all patients exhibit ocular abnormalities and pruritus. Electro-encephalography shows a slow background activity, without other abnormalities. MRI of the brain shows an arrest of myelination, periventricular signal abnormalities of white matter and mild ventricular enlargement. Cerebral (1)H-MR spectroscopy reveals a characteristic, abnormal lipid peak. The degree of white matter abnormality in the MRIs and the height of the lipid peak in (1)H-MR spectra do not correlate with the severity of the neurological signs. The clinical presentation and the clinical course is strikingly similar in these patients. Patient 18 shows a mild phenotype that essentially contains the same, but less severe, clinical features. Patient 19 exhibits the typical, but very mild, dermatological and ocular abnormalities, without any clinical neurological involvement. The diagnosis of SLS was confirmed by demonstration of the enzyme defect in cultured skin fibroblasts. Furthermore, as might be predicted from the essential role of FALDH in leucotriene B(4) (LTB(4)) metabolism, elevated urinary concentrations of LTB(4) and 20-OH-LTB(4) were found in all patients studied. Molecular studies of the FALDH gene revealed eight different mutations, including three new ones: a large 26-base pair deletion (21-46del), a missense mutation (80C-->T) and an insertion mutation (487-488insA). The vast majority of SLS patients seem to be severely affected independent of their genotype.

Identification of pristanal dehydrogenase activity in peroxisomes: conclusive evidence that the complete phytanic acid alpha-oxidation pathway is localized in peroxisomes

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched-chain fatty acid which, due to the methyl-group at the 3-position, can not undergo beta-oxidation unless the terminal carboxyl-group is removed by alpha-oxidation. The structure of the phytanic acid alpha-oxidation machinery in terms of the reactions involved, has been resolved in recent years and includes a series of four reactions: (1) activation of phytanic acid to phytanoyl-CoA, (2) hydroxylation of phytanoyl-CoA to 2-hydroxyphytanoyl-CoA, (3) cleavage of 2-hydroxyphytanoyl-CoA to pristanal and formyl-CoA, and (4) oxidation of pristanal to pristanic acid. The subcellular localization of the enzymes involved has remained enigmatic, with the exception of phytanoyl-CoA hydroxylase and 2-hydroxyphytanoyl-CoA lyase which are both localized in peroxisomes. The oxidation of pristanal to pristanic acid has been claimed to be catalysed by the microsomal aldehyde dehydrogenase FALDH encoded by the ALDH10-gene. Making use of mutant fibroblasts deficient in FALDH activity, we show that phytanic acid alpha-oxidation is completely normal in these cells. Furthermore, we show that pristanal dehydrogenase activity is not fully deficient in FALDH-deficient cells, implying the existence of one or more additional aldehyde dehydrogenases reacting with pristanal. Using subcellular localization studies, we now show that peroxisomes contain pristanal dehydrogenase activity which leads us to conclude that the complete phytanic acid alpha-oxidation pathway is localized in peroxisomes.

The first case of 4-hydroxybutyric aciduria in Japan

We report a boy with 4-hydroxybutyric aciduria resulting from a deficiency of succinic semialdehyde dehydrogenase (SSADH). A boy, 1 year 5 months, showed delayed walk with hypotonia and could not speak meaningful words. The blood levels of lactate, pyruvate and amino acids were not elevated. Head magnetic resonance imaging (MRI) and electroenchephalography (EEG) were normal. Urinary organic acid analysis with gas chromatography-mass spectrometry (GCMS) revealed increased levels of 4-hydroxybutyric acid, glutaric acid, adipic acid and suberic acid. The concentrations of 4-hydroxybutyric acid and gamma-aminobutyric acid (GABA) were elevated in the serum and cerebrospinal fluid (CSF). SSADH activity in cultured lymphoblasts was 4.5% of the normal level. So far as we know this is the first Japanese patient diagnosed as 4-hydroxybutyric acid. Urinary organic acid analysis is necessary for the diagnosis of patients with unexplained psychomotor retardation.

Prenatal diagnosis of succinic semialdehyde dehydrogenase deficiency: increased accuracy employing DNA, enzyme, and metabolite analyses

Inherited succinic semialdehyde dehydrogenase (SSADH; EC1.2.1.24; McKusick 271980) deficiency is a defect of GABA degradation which leads to accumulation of 4-hydroxybutyric acid (gamma-hydroxybutyric acid; GHB) in physiologic fluids of patients. Prenatal diagnosis (PND) was performed in three at-risk pregnancies employing combinations of: (1) reverse-transcription-polymerase chain reaction (RT-PCR) and genomic DNA amplification followed by sequencing using isolated leukocytes or cultured human lymphoblasts; (2) GHB quantitation in amniotic fluid; or (3) SSADH enzyme assay in chorionic villus (CV) and/or amniocytes. In two pregnancies, all analyses were concordant for prediction of disease status in the fetus. In the third case, enzyme activity in CV (deficient) and metabolite analysis in amniotic fluid (normal) were discordant. For clarification, mutation analysis was undertaken in CV, confirming heterozygosity for the mutation previously identified in the proband. We hypothesize that delayed transit time for shipment of CV between Greece and the United States (8 days) led to enhanced degradation of heterozygous SSADH enzyme activity. Our data demonstrate the importance of combined metabolite, enzyme, and DNA analysis for increased accuracy in the PND of SSADH deficiency.

Microsomal fatty aldehyde dehydrogenase catalyzes the oxidation of aliphatic aldehyde derived from ether glycerolipid catabolism: implications for Sjögren-Larsson syndrome

The enzyme that catalyzes the oxidation of fatty aldehyde derived from ether glycerolipid catabolism has not been identified. To determine whether microsomal fatty aldehyde dehydrogenase (FALDH) is responsible, we investigated the metabolism of 1-O-[9, 10-(3)H-octadecyl]-glycerol ([(3)H]OG) in FALDH-deficient cultured cells from patients with Sjögren-Larsson syndrome (SLS) and in mutant Chinese hamster ovary (CHO) cells. Intact fibroblasts from SLS patients incubated with [(3)H]OG showed a selective deficiency (38+/-7% of normal) in the incorporation of radioactivity into fatty acid, but no decrease in incorporation of radioactivity into fatty alcohol, total lipids and phosphatidylethanolamine (PE). Consistent with fatty aldehyde accumulation, incorporation of radioactivity into N-alkyl-phosphatidylethanolamine, which is derived from Schiff base formation of free aldehyde with PE, was 4-fold higher in SLS fibroblasts compared to normal controls. Similar results were seen with SLS keratinocytes, whereas FALDH-deficient CHO cells showed a more profound reduction in radioactive fatty acid to 12+/-2% of normal. These results implicate FALDH in the oxidation of ether-derived fatty aldehyde in human and rodent cells. Metabolism of ether glycerolipids is a previously unrecognized source of fatty aldehyde that may contribute to the pathogenesis of SLS.

Juvenile macular dystrophy associated with deficient activity of fatty aldehyde dehydrogenase in Sjögren-Larsson syndrome

PURPOSE

To report the ocular manifestations associated with the Sjögren-Larsson syndrome in a series of patients with proven fatty aldehyde dehydrogenase deficiency. To emphasize the clinical importance of the ophthalmological features of the Sjögren-Larsson syndrome. To discuss the metabolic disturbances that might give rise to the ophthalmological picture.

METHODS

Fifteen patients with Sjögren-Larsson syndrome underwent a standardized ophthalmological examination. In patients of appropriate age, and who were able to cooperate, additional investigations were performed.

RESULTS

All patients exhibited bilateral, glistening yellow-white crystalline deposits that were located in the innermost retinal layers and appeared during the first 2 years of life. Repeated fundus photography in individual patients showed that the dots became more numerous as the patients got older. Photophobia, subnormal visual acuity, myopia, and astigmatism were found in most of the patients. Fluorescein angiography was performed in three patients and showed a mottled hyperfluorescence of the retinal pigment epithelium, without leakage. Color vision, electroretinography, and electro-oculography could be performed in only a small number of patients and showed no abnormalities. Visual evoked potentials were found to be abnormal in six of eight patients.

CONCLUSIONS

In Sjögren-Larsson syndrome, patients exhibit highly characteristic bilateral, glistening yellow-white retinal dots from the age of 1 to 2 years onward. The number of dots increases with age. The extent of the macular abnormality does not correlate with the severity of the ichthyosis or with the severity of the neurological abnormalities. A high percentage of patients shows additional ocular signs and symptoms, notably marked photophobia.

Molecular characterization of methylmalonate semialdehyde dehydrogenase deficiency

Three patients have been reported with (putative) methylmalonic semialdehyde dehydrogenase (MMSDH) deficiency. The urine metabolic pattern was strikingly different in all, including beta-alanine, 3-hydroxypropionic acid, both isomers of 3-amino- and 3-hydroxyisobutyric acids in one and 3-hydroxyisobutyric and lactic acids in a second, and mild methylmalonic aciduria in a third patient. In an effort to clarify these disparate metabolite patterns, we completed the cDNA structure, and characterized the genomic structure of human MMSDH gene in order to undertake molecular analysis. Only the first patient had alterations in the MMSDH coding region, revealing homozygosity for a 1336G > A transversion, which leads to substitution of arginine for highly conserved glycine at amino acid 446. No abnormalities of the MMSDH cDNA were detected in the other patients. These data provide the first molecular characterization of an inborn error of metabolism specific to the L-valine catabolic pathway.

[Sjögren-Larsson syndrome]

This rare, ubiquitous neurocutaneous disorder is inherited in an autosomal recessive fashion. Its primary clinical manifestations are congenital ichthyosis, spastic diplegia or tetraplegia, and mental retardation. The causative biochemical defect has been identified as a deficiency of the enzyme fatty aldehyde dehydrogenase, a component of fatty alcohol:NAD+ oxidoreductase. We present a case report of an affected 3.5 year old white girl to give an overview of the pre- and postnatal diagnostic procedures as well as of therapeutic options.

Stereodifferentiation of 3-hydroxyisobutyric- and 3-aminoisobutyric acid in human urine by enantioselective multidimensional capillary gas chromatography-mass spectrometry

The chiral metabolites 3-hydroxyisobutyric acid (HIBA) and 3-aminoisobutyric acid (AIBA) are intermediates in the pathways of L-valine and thymine and play an important role in the diagnosis of the very rare inherited metabolic diseases 3-hydroxyisobutyric aciduria (McKusick 236975) and methylmalonic semialdehyde dehydrogenase deficiency (McKusick 603178-MSDD). Until now only a few approaches have been made in enantioselective analysis of HIBA and AIBA and for that reason very little information is available on enantiomeric ratios of these metabolites in man. This paper reports on the simultaneous stereodifferentiation of HIBA and AIBA in human urine as corresponding N(O)-methoxycarbonyl methyl esters by derivatization with methyl chloroformate (MCF) using enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC/MS) with heptakis-(2, 3-di-O-methyl-6-O-tert.-butyl-dimethylsilyl)-beta-cyclodextrin as the chiral stationary phase. During this investigation urine samples from different patients and healthy controls were analyzed in order to reveal characteristic enantiomeric patterns of these metabolites. A trend of dominating R-HIBA excretion in the control urine samples investigated was observed. An excretion of more than 80% S-HIBA was found in the urines of two patients with ketonemic vomiting. There are some clues indicating a possible renal reabsorbtion of S-HIBA similar to those of S-AIBA. Furthermore, there was a significant finding with regard to the enantiomeric distribution of AIBA in a patient with MSDD - a markedly increased excretion of the S-enantiomer in contrast to the other samples. Using the enantiomeric ratios of AIBA, a previously investigated case of benign methylmalonic aciduria (bMMA) could be excluded from the diagnosis of MSDD.

5-Lipoxygenase inhibition: a new treatment strategy for Sjögren-Larsson syndrome

The Sjögren-Larsson syndrome (SLS) is a severe neurocutaneous disorder due to fatty aldehyde dehydrogenase (FALDH) deficiency. The recent discovery of the role of FALDH in the degradation of leukotriene B4 (LTB4) opened the way to the development of a new therapeutic strategy for SLS, i.e. 5-lipoxygenase inhibition. We treated one SLS patient with zileuton during five weeks. During the treatment period we found decreased values of LTB4 and omega-OH-LTB4. The severity of the pruritus diminished, and favorable changes in the child's behavior were observed. The height of the prominent "lipid peak" of cerebral white matter (that is characteristically found on proton magnetic resonance spectroscopy in SLS patients) decreased during treatment, and increased again when treatment was stopped. In conclusion, the beneficial effects of 5-lipoxygenase inhibition in SLS are very promising and encourage further research.

Proton MR spectroscopy of Sjögren-Larsson's syndrome

We performed single-voxel proton MR spectroscopy (1H-MRS) in two children with Sjögren-Larsson's syndrome (SLS). Both patients showed two abnormal spectral peaks at 1.3 ppm and 0.9 ppm that were obtained with short echo times. These two abnormal spectral peaks were seen in high-intensity areas on T2-weighted images and also in basal ganglia of normal intensities. 1H-MRS may be useful for establishing the diagnosis and investigating the natural history of SLS, and for evaluating the efficacy of therapeutic approaches to SLS.

Sjögren-Larsson syndrome: clinical and MRI/MRS findings in FALDH-deficient patients

OBJECTIVE

To determine the spectrum of clinical and MRI/1H MRS features of patients with fatty aldehyde dehydrogenase (FALDH) deficiency.

BACKGROUND

The Sjogren-Larsson syndrome (SLS) was originally defined as a clinical triad consisting of ichthyosis, spastic di- or tetralegia, and mental retardation, with autosomal recessive inheritance. By now, both the deficiency of the enzyme FALDH, and the genetic mutations on chromosome 17 responsible for this deficiency, have been identified. SLS, defined by fibroblast FALDH deficiency, seems to be a much broader syndrome.

METHODS

The clinical findings of 11 FALDH-deficient patients of different ages and one patient with the characteristic SLS-like ichthyosis, but without FALDH deficiency, were evaluated in relation to their cerebral MRI, and to 1H MRS in six patients.

RESULTS

The severity of neurologic symptoms showed considerable variation. Fundoscopic perifoveal glistening dots and the characteristic SLS-like ichthyosis were present in all patients. Serial MRI findings showed evidence of retarded myelination and a variable degree of dysmyelination. 1H MRS showed an accumulation of free lipids in the periventricular white matter, even before the stage of visible dysmyelination.

CONCLUSIONS

The neurologic consequences of FALDH deficiency show considerable variation. The characteristic pattern of ichthyosis and retinal degeneration are seen consistently, yet they are not pathognomonic. MRI and 1H MRS findings suggest an accumulation of long-chain fatty alcohol intermediates, resulting in retarded myelination and dysmyelination.