Fatty aldehyde and fatty alcohol metabolism: review and importance for epidermal structure and function

Normal fatty aldehyde and alcohol metabolism is essential for epidermal differentiation and function. Long-chain aldehydes are produced by catabolism of several lipids including fatty alcohols, sphingolipids, ether glycerolipids, isoprenoid alcohols and certain aliphatic lipids that undergo α- or ω-oxidation. The fatty aldehyde generated by these pathways is chiefly metabolized to fatty acid by fatty aldehyde dehydrogenase (FALDH, alternately known as ALDH3A2), which also functions to oxidize fatty alcohols as a component of the fatty alcohol:NAD oxidoreductase (FAO) enzyme complex. Genetic deficiency of FALDH/FAO in patients with Sjögren-Larsson syndrome (SLS) results in accumulation of fatty aldehydes, fatty alcohols and related lipids (ether glycerolipids, wax esters) in cultured keratinocytes. These biochemical changes are associated with abnormalities in formation of lamellar bodies in the stratum granulosum and impaired delivery of their precursor membranes to the stratum corneum (SC). The defective extracellular SC membranes are responsible for a leaky epidermal water barrier and ichthyosis. Although lamellar bodies appear to be the pathogenic target for abnormal fatty aldehyde/alcohol metabolism in SLS, the precise biochemical mechanisms are yet to be elucidated. Nevertheless, studies in SLS highlight the critical importance of FALDH and normal fatty aldehyde/alcohol metabolism for epidermal function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

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.

Sjögren-Larsson syndrome

Sjögren-Larsson syndrome is a recessively inherited syndrome caused by deficiency of fatty aldehyde dehydrogenase. The most common symptoms and signs are described, especially ichthyosis, spastic diplegia, and severe learning difficulties; but also other less frequent ones. Special investigations include sensory evoked potentials, electromyography, and proton magnetic resonance spectroscopy. Post-mortem examination shows, in particular, an accumulation of lipid substances in specific regions of the brain. The diagnosis depends on the measurement of fatty aldehyde dehydrogenase in cultured fibroblasts from skin biopsies, and by identifying known mutations by allele-specific polymerase chain reaction assay. Prenatal diagnosis is possible by using the same technique. The disorder is located on gene 17, and many mutations have been identified. Most mutations are unique to an affected family, but clinical variations may be due to unknown genetic and environmental factors. The deficiency of the enzyme impairs the oxidation of medium and long chain fatty aldehydes, and this may explain the link between the brain and skin disorders. The treatment of affected children needs input from a number of specialists, and their contributions are discussed.

Ichthyosis in Sjögren-Larsson syndrome reflects defective barrier function due to abnormal lamellar body structure and secretion

Sjögren-Larsson syndrome is a genetic disease characterized by ichthyosis, mental retardation, spasticity and mutations in the ALDH3A2 gene coding for fatty aldehyde dehydrogenase, an enzyme necessary for oxidation of fatty aldehydes and fatty alcohols. We investigated the cutaneous abnormalities in 9 patients with Sjögren-Larsson syndrome to better understand how the enzymatic deficiency results in epidermal dysfunction. Histochemical staining for aldehyde oxidizing activity was profoundly reduced in the epidermis. Colloidal lanthanum perfusion studies showed abnormal movement of tracer into the extracellular spaces of the stratum corneum consistent with a leaky water barrier. The barrier defect could be attributed to the presence of abnormal lamellar bodies, many with disrupted limiting membranes or lacking lamellar contents. Entombed lamellar bodies were present in the cytoplasm of corneocytes suggesting blockade of lamellar body secretion. At the stratum granulosum-stratum corneum interface, non-lamellar material displaced or replaced secreted lamellar membranes, and in the stratum corneum, the number of lamellar bilayers declined and lamellar membrane organization was disrupted by foci of lamellar/non-lamellar phase separation. These studies demonstrate the presence of a permeability barrier abnormality in Sjögren-Larsson syndrome, which localizes to the stratum corneum interstices and can be attributed to abnormalities in lamellar body formation and secretion.

Ultrastructural study of the skin in Sjögren-Larsson syndrome

The ichthyosiform skin and the uninvolved skin of a 5-year-old Japanese female with Sjögren-Larsson syndrome were examined by light and electron microscopy to elucidate the keratinization disorder. Light microscopically, the epidermis of the ichthyosiform skin showed acanthosis, papillomatosis and hyperkeratosis. The horny cells had a basket-weave appearance. The granular cell layer was slightly thickened. Slight round cell infiltration and vascular dilatation were seen in the upper dermis. The uninvolved skin was histologically normal. Electron microscopically, in both ichthyosiform and uninvolved skin, abnormal lamellar or membranous inclusions were present in the cytoplasm of horny cells of the epidermis. These inclusions appeared to be derived from some of the lamellar bodies and/or abnormal membranous structures found in the cytoplasm of spinous and granular cells. Mitochondria in the epidermal basal cells were more numerous in the ichthyosiform skin than in the uninvolved skin. These findings indicate that, whether the skin is involved or not, the epidermis of the patient with this disorder may always have a structural abnormality, which may be genetically determined. Local environmental factors may play a role in inducing the acanthosis and papillomatosis of the epidermis.

Depletion of alcohol (hexanol) dehydrogenase activity in the epidermis and jejunal mucosa in Sjögren-Larsson syndrome

Using a histochemical technique, we have demonstrated a consistent deficiency of alcohol (hexanol) dehydrogenase activity within the epidermis and jejunal mucosa of patients with Sjögren-Larsson syndrome. Biochemical assay of the fatty alcohol: NAD oxidoreductase activity in cultured fibroblasts and leukocytes from these patients showed deficient activities compared with controls. The histochemical and biochemical results are complementary, and the simpler histochemical method can be used reliably for initial screening of patients with ichthyosis in whom a diagnosis of Sjögren-Larsson syndrome is suspected.

Phenotypic variability among adult siblings with Sjögren-Larsson syndrome

BACKGROUND

Sjögren-Larsson syndrome (SLS) is an early childhood-onset disorder with ichthyosis, mental retardation, spastic paraparesis, macular dystrophy, and leukoencephalopathy caused by the deficiency of fatty aldehyde dehydrogenase due to mutations in the ALDH3A2 gene (the gene that encodes microsomal fatty aldehyde dehydrogenase). Cerebral proton magnetic resonance spectroscopy in those with SLS demonstrates an abnormal white matter peak at 1.3 ppm, consistent with long-chain fatty alcohol accumulation.

OBJECTIVE

To define the clinical course and proton magnetic resonance spectroscopic findings of SLS in adults.

DESIGN AND SETTING

Case series in a tertiary care center.

PATIENTS

Six siblings of a consanguineous Arab family with early childhood-onset SLS who carry the 682C-->T mutation in the ALDH3A2 gene were reinvestigated in adulthood.

RESULTS

The 6 affected siblings ranged in age from 16 to 36 years. All exhibited the typical clinical and imaging manifestations of SLS, but their severity markedly varied. Neurological involvement was apparently nonprogressive, and its severity showed no correlation with age. Cerebral proton magnetic resonance spectroscopy showed a lipid peak at 1.3 ppm, with decreasing intensity in the older siblings.

CONCLUSION

These observations document significant clinical variability and the nonprogressive neurological course of SLS in adult siblings with the same ALDH3A2 genotype, and demonstrate possible correlation of proton magnetic resonance spectroscopic changes with age, suggesting unknown pathogenic mechanisms to compensate for the responsible biochemical defect in this disease.

Cerebral MRI and spectroscopy in Sjögren-Larsson syndrome: case report

We report MRI and MRS of the brain in a patient with Sjögren-Larsson syndrome (SLS) in whom fatty alcohol oxidoreductase (FAO) deficiency has been verified. MRI showed periventricular lesions, high intensity on T2-weighted and low intensity on T1-weighted images at trigones of the lateral ventricles. 1H-MRS of these lesions revealed high lipid and low N-acetyl aspartate peaks. We presume such lipids in periventricular lesions with high T2 signal may be pathognomonic of SLS.

Disturbed brain ether lipid metabolism and histology in Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS) is a rare neurometabolic syndrome caused by deficient fatty aldehyde dehydrogenase. Patients exhibit intellectual disability, spastic paraplegia, and ichthyosis. The accumulation of fatty alcohols and fatty aldehydes has been demonstrated in plasma and skin but never in brain. Brain magnetic resonance imaging and spectroscopy studies, however, have shown an abundant lipid peak in the white matter of patients with SLS, suggesting lipid accumulation in the brain as well. Using histopathology, mass spectrometry imaging, and lipidomics, we studied the morphology and the lipidome of a postmortem brain of a 65-year-old female patient with genetically confirmed SLS and compared the results with a matched control brain. Histopathological analyses revealed structural white matter abnormalities with the presence of small lipid droplets, deficient myelin, and astrogliosis. Biochemically, severely disturbed lipid profiles were found in both white and gray matter of the SLS brain, with accumulation of fatty alcohols and ether lipids. Particularly, long-chain unsaturated ether lipid species accumulated, most prominently in white matter. Also, there was a striking accumulation of odd-chain fatty alcohols and odd-chain ether(phospho)lipids. Our results suggest that the central nervous system involvement in SLS is caused by the accumulation of fatty alcohols leading to a disbalance between ether lipid and glycero(phospho)lipid metabolism resulting in a profoundly disrupted brain lipidome. Our data show that SLS is not a pure leukoencephalopathy, but also a gray matter disease. Additionally, the histopathological abnormalities suggest that astrocytes and microglia might play a pivotal role in the underlying disease mechanism, possibly contributing to the impairment of myelin maintenance.

Large contiguous gene deletions in Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS) is an autosomal recessive disorder characterized by ichthyosis, mental retardation, spasticity and mutations in the ALDH3A2 gene for fatty aldehyde dehydrogenase, an enzyme that catalyzes the oxidation of fatty aldehyde to fatty acid. More than 70 mutations have been identified in SLS patients, including small deletions or insertions, missense mutations, splicing defects and complex nucleotide changes. We now describe 2 SLS patients whose disease is caused by large contiguous gene deletions of the ALDH3A2 locus on 17p11.2. The deletions were defined using long distance inverse PCR and microarray-based comparative genomic hybridization. A 24-year-old SLS female was homozygous for a 352-kb deletion involving ALDH3A2 and 4 contiguous genes including ALDH3A1, which codes for the major soluble protein in cornea. Although lacking corneal disease, she showed severe symptoms of SLS with uncommon deterioration in oral motor function and loss of ambulation. The other 19-month-old female patient was a compound heterozygote for a 1.44-Mb contiguous gene deletion and a missense mutation (c.407C>T, P136L) in ALDH3A2. These studies suggest that large gene deletions may account for up to 5% of the mutant alleles in SLS. Geneticists should consider the possibility of compound heterozygosity for large deletions in patients with SLS and other inborn errors of metabolism, which has implications for carrier testing and prenatal diagnosis.

MRI and ¹H-MRS findings of three patients with Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS) is a rare autosomal recessive neurocutaneous disorder caused by deficiency of the microsomal enzyme fatty aldehyde dehydrogenase. Patients present the classical triad of congenital ichthyosis, mental retardation and spastic di- or tetraplegia. Magnetic resonance imaging (MRI) of the brain usually shows hypomyelination involving the periventricular white matter. Cerebral proton MR spectroscopy (¹H-MRS) reveals a characteristic abnormal lipid peak. We report three cases of SLS from different families with the typical clinical triad. The MRI and ¹H-MRS findings are discussed.

Update on Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS, MIM 270200) is a rare autosomal recessive neurocutaneous disorder due to a deficiency of the fatty aldehyde dehydrogenase and defined by a characteristic triad of symptoms including congenital ichthyosis, spastic di- or quadriplegia and mental retardation. Recently, genetic studies have subsequently shown linkage of the syndrome to chromosome 17p in Swedish pedigrees, confirmation of linkage to the same locus in non-Swedish pedigrees, and finally cloning of the gene as well as detection of mutations in affected probands. Furthermore, SLS may well be soon added to the list of peroxisomal disorders. The purpose of this paper is to provide an up-to-date synopsis of SLS and to outline specific aspects of this syndrome that are still unclear.

Novel and recurrent ALDH3A2 mutations in Italian patients with Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS; MIM#270200) is an autosomal recessive neurocutaneous disease caused by mutations in the ALDH3A2 gene for fatty aldehyde dehydrogenase (FALDH), a microsomal enzyme that catalyzes the oxidation of medium- and long- chain aliphatic aldehydes fatty acids. We studied two unrelated Italian SLS patients with ichthyosis, developmental delay, spastic diplegia and brain white matter disease. One patient was homozygous for a novel ALDH3A2 insertion mutation (c.767insA) in exon 5. The other SLS patient was a compound heterozygote for two previously reported mutations: a slice site mutation (c.1094C > T; S365L) in exon 7. Analysis of fibroblast RNA by RT-PCR indicated that the spice-site mutation caused skipping of exons 2 and 3. The c.1094C > T mutation, previously associated with two ALDH3A2 haplotypes, was found on a third distinct haplotype in our patient, which indicates that arose independently in this kindred. These results add to understanding of the genetic basis of SLS and will be useful for DNA diagnosis of this disease.

Sjögren-Larsson syndrome: postmortem brain abnormalities

Brain abnormalities were described in a patient who had experienced Sjogren-Larsson syndrome (SLS) with typical clinical signs. Examination of the brain revealed (1) accumulation of peculiar lipoid substances stained lightly with periodic acid-Schiff (PAS) in the subpial, subependymal, and perivascular glial layers, the subpial and perivascular spaces, and the white matter of the cerebrum and brainstem; (2) proliferation of perivascular macrophages containing lipofuscin-like pigments; (3) dense distribution of round or ellipsoid small bodies stained strongly with PAS in the subpial, subependymal, and perivascular glial layers and the white matter; (4) appearance of spheroid bodies in the neuropil of relay nuclei (the lateral geniculate body, pontine nuclei, inferior olivary nucleus, posterior funicular nucleus, and dentate nucleus) and the white matter; and (5) reduction of myelinated nerve fibers in the cerebral and cerebellar white matter. Six-layered neuronal cytoarchitecture was preserved in the cerebral neocortex, except for the insula where pyramidal neurons were arranged at random. The exact mechanisms remain unclear, but it is suggested that peculiar lipoid substances may accumulate in the specific regions of the brain and that neuronal and astrocytic processes may be primarily affected in SLS.

Monoaminergic dysfunction in Sjögren-Larsson syndrome

The anteroposterior distribution of monoamine and monoamine metabolite concentrations was determined in subcortical brain nuclei of two cases of Sjögren-Larsson syndrome (SLS) and was compared to two control cases. The brains were divided into halves and sectioned coronally. For biochemical analyses, caudate nucleus, putamen, globus pallidus, substantia nigra, nucleus accumbens, amygdala, and hippocampus were dissected macroscopically. Monoamine and its metabolites were determined by reverse-phase liquid chromatography with electrochemical detection. The other hemisphere was studied neuropathologically. The SLS cases revealed cell loss in substantia nigra and putamen and a widespread white-matter destruction. Biochemically, most pronounced alterations were seen in the dopamine system in putamen with severely reduced concentrations of dopamine (DA; 14% of control values) and the catabolic metabolites 3-methoxytyramine (3-MT; 9% of control values) and homovanillic acid (HVA; 20% of control values). In substantia nigra and the other striatal regions studied, a general decrease of 3-MT and HVA concentrations was observed in the SLS subjects compared to the controls, although the decrease was less pronounced than in putamen. Generally, somewhat reduced noradrenaline and 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations were seen in the SLS cases, whereas serotonin and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were increased compared to the controls in most regions studied. These data suggest a specific monoaminergic dysfunction in patients with SLS. The severe decline in the dopaminergic system in putamen suggests that supplementation of dopamine agonists may ameliorate the symptoms of SLS patients.

Sjögren-Larsson syndrome: novel mutations in the ALDH3A2 gene in a French cohort

Sjogren-Larsson syndrome (SLS) is a rare autosomal recessive disorder characterized by ichthyosis, spastic di- or tetraplegia and mental retardation due a defect of the fatty aldehyde dehydrogenase (FALDH), related to mutations in the ALDH3A2 gene. In this study, we screened a French cohort of patients with Sjögren-Larsson syndrome (SLS) for mutations in the ALDH3A2 gene. The five unrelated patients with typical SLS all present mutations in this gene. Three novel mutations were identified whereas three other ones were previously described. We also realized functional analyses at the mRNA level for two splice site mutations to study their deleterious consequences. Two of the previously described mutations had already been identified in the same region of Europe, suggesting a putative founder effect. We suggest that, (1) when clinical and MR features are present, direct sequencing of the ALDH3A2 gene in SLS is of particular interest without necessity of a skin biopsy for enzymatic assay in order to propose genetic counsel and (2) identification of mutations already described in the same population with putative founder effects may simplify genetic analysis in this context.

Incomplete Sjögren-Larsson syndrome in two Japanese siblings

Sjögren-Larsson syndrome (SLS) is a rare, autosomal recessive disorder characterized by ichthyosis, spastic diplegia and mental retardation. Biochemical studies have pinpointed the pathogenesis resulting in the deficiency of the fatty aldehyde dehydrogenase (FALDH) component of the fatty alcohol NAD+ oxidoreductase complex. Histochemical analysis revealed a reduction in alcohol dehydrogenase (AD) activity in the skin. SLS patients have been categorized biochemically into two groups: complete and incomplete reduction according to the degree of FALDH deficiency. Our patients demonstrated incomplete clinical features, including a 1/3 reduction in FALDH activity, and decreased AD activity in the ichthyotic lesion. The phenotypical differences between our cases and classic SLS are probably due to the partial FALDH deficiency.

MR spectroscopy and diffusion tensor imaging of the brain in Sjögren-Larsson syndrome

Diffusion tensor imaging (DTI) is reported for the first time in a patient with Sjögren-Larsson syndrome, an autosomal recessive neurocutaneous disorder. Magnetic resonance spectroscopy (MRS) revealed normal levels of choline, creatine and N-acetyl aspartate (NAA) and the characteristic lipid signals in the white matter brain tissue. Conventional MRI showed increased signal intensity around the lateral ventricles indicating abnormal myelination. DTI revealed normal apparent diffusion coefficient (ADC) values, but reduced fractional anisotropy (FA) in the white matter. After co-registration of the parameters obtained with DTI with the results of MRS (36 voxels), significant correlations were obtained of lipid content with FA (r=0.81), ADC (r=-0.62), choline (r=0.51), and NAA (r=0.44) (P<0.01, all). These results suggest that in Sjögren-Larsson syndrome, the white matter lipid signals originate from the neurons, with NAA and choline reflecting neuron density and myelination. The comparatively high FA/low ADC values in these lipid-rich locations, indicate a loss of diffusion in directions perpendicular to the fibers. The overall loss of FA in the white matter may reflect a loss of brain tissue water content in SLS patients compared with controls and precede the formation of atrophy.

Sjögren-Larsson syndrome: case reports of two brothers

Sjögren-Larsson syndrome (SLS) is an autosomal recessively inherited disorder characterized by the triad of congenital ichthyosis, spastic diplegia or tetraplegia and mental retardation. SLS is also often associated with a variety of other anomalies, including signs that are of interest to optometrists and ophthalmologists. Two case histories are presented. Both patients exhibited maculopathies and uncorrected astigmatism. The reduced visual acuities in one case appeared to be caused at least partly by astigmatism and the associated astigmatic amblyopia.

AA, Alotaibi M, Asseri H, Bokari KA. Sjogren-Larsson Syndrome: A case series of five members from an extended family with a novel mutation

BACKGROUNDD

Sjogren-Larsson syndrome (SLS) is a rare autosomal recessive disorder, characterized by a triad of spastic tetraplegia or diplegia, congenital ichthyosis, and intellectual disability.

METHODS

We report a seven-years-old female born to consanguineous parents who presented with erythematous dry scaly skin all over the body sparing the face, without collodion membrane which started since birth. There were associated with global developmental delay and seizure disorder. SLS was suspected and hence sequence analysis of the ALDH3A2 gene by next-generation sequencing was performed for the patient.

RESULTS

A novel nucleotide exchange in homozygous state at position c.1320 in exon 9 of the ALDH3A2 gene (c.1320T>A), leading to a stop of the protein sequence (p.Tyr440) was detected in the patient. Genetic testing of the patient's extended family revealed another four affected family members with the same mutation.

CONCLUSIONS

SLS should be suspected in any patient with a triad of ichthyosis, intellectual disability and spastic di/tetraplegia. Molecular genetic testing of the ALDH3A2 gene should be performed to confirm the diagnosis. Extended family screening is highly recommended.