The design of a diet restricted in saturated very long-chain fatty acids: therapeutic application in adrenoleukodystrophy

Nutritional status of children affected by X-linked adrenoleukodystrophy

BACKGROUND

Adrenoleukodystrophy (ALD) is a rare X-linked metabolic disorder that causes the accumulation of very-long-chain fatty acids (VLCFAs) (C26:0) and the subsequent variety of clinical and neurological symptoms. Little is known about nutritional status and dietary habits of children affected by ALD, and so the present study aimed to assess nutritional status and food intake in children with ALD, also exploring the relationship between food intake and the consumption of disease-specific dietary supplements to reduce blood C26:0 concentrations and increase monounsaturated fatty acids (C26:1).

METHODS

All patients underwent a clinical and neurological evaluation and a comprehensive nutritional assessment. The association of VLCFA concentrations with dietary lipids was assessed.

RESULTS

Nine boys (11.49 ± 3.61 years) were enrolled in a cross-sectional study. All patients were normal weight, with normal resting energy expenditure. Only six of nine patients followed the low-fat diet and dietary supplements. An inverse association was found between the food intake of polyunsaturated lipids and C26:0; conversely, the C26:0 was positively associated with the dietary saturated lipids. When consumed, dietary supplement consumption correlated positively with C26:1 (ρ = 0.917, p = 0.029) and no correlation was found with C26:0 (ρ = 0.410, p = 0,493).

CONCLUSIONS

No children were found to be malnourished or overweight or obese; however, half of the children reported excessive body fat, probably as a result of the pharmacotherapies. A low-fat diet could be adjuvant in the management of the accumulation of VLCFAs, but poor dietary compliance to disease-specific nutritional guidelines appears to be a major problem of this condition and underlines the need for a structured and personalised nutritional management in ALD disease.

Newborn screening for X-linked adrenoleukodystrophy in Italy: Diagnostic algorithm and disease monitoring

Introduction

X-linked adrenoleukodystrophy (X-ALD) is the most common inherited peroxisomal disorder caused by variants in the ABCD1 gene. The main phenotypes observed in men with X-ALD are primary adrenal insufficiency, adrenomyeloneuropathy, and cerebral ALD (cALD). Cerebral ALD consists of a demyelinating progressive cerebral white matter (WM) disease associated with rapid clinical decline and is fatal if left untreated. Hematopoietic stem cell transplantation is the standard treatment for cALD as it stabilizes WM degeneration when performed early in the disease. For this reason, early diagnosis is crucial, and several countries have already implemented their newborn screening programs (NBS) with the assessment of C26:0-lysophosphatidylcholine (C26:0-LPC) values as screening for X-ALD.

Methods

In June 2021, an Italian group in Lombardy launched a pilot study for the implementation of X-ALD in the Italian NBS program. A three-tiered approach was adopted, and it involved quantifying the values of C26:0-LPC and other metabolites in dried blood spots with FIA-MS/MS first, followed by the more specific ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) technique and, finally, the genetic confirmation via focused NGS.

Discussion

Genetically confirmed patients are set to undergo a follow-up protocol and are periodically evaluated to promptly start a specific treatment if and when the first signs of brain damage appear, as suggested by international guidelines. A specific disease monitoring protocol has been created based on literature data and personal direct experience.

Conclusion

The primary aim of this study was to develop a model able to improve the early diagnosis and subsequent follow-up and timely treatment of X-ALD.

Ethics

The study was approved by the local ethics committee. The research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest.

Peroxisome biogenesis disorders in the Zellweger spectrum: An overview of current diagnosis, clinical manifestations, and treatment guidelines

Peroxisome biogenesis disorders in the Zellweger spectrum (PBD-ZSD) are a heterogeneous group of genetic disorders caused by mutations in PEX genes responsible for normal peroxisome assembly and functions. As a result of impaired peroxisomal activities, individuals with PBD-ZSD can manifest a complex spectrum of clinical phenotypes that typically result in shortened life spans. The extreme variability in disease manifestation ranging from onset of profound neurologic symptoms in newborns to progressive degenerative disease in adults presents practical challenges in disease diagnosis and medical management. Recent advances in biochemical methods for newborn screening and genetic testing have provided unprecedented opportunities for identifying patients at the earliest possible time and defining the molecular bases for their diseases. Here, we provide an overview of current clinical approaches for the diagnosis of PBD-ZSD and provide broad guidelines for the treatment of disease in its wide variety of forms. Although we anticipate future progress in the development of more effective targeted interventions, the current guidelines are meant to provide a starting point for the management of these complex conditions in the context of personalized health care.

Peanut consumption increases levels of plasma very long chain fatty acids in humans

Peanut consumption has been suspected of raising plasma very long chain fatty acid (VLCFA) levels in humans. The effect of peanut consumption on VLCFAs was studied in six human subjects. After 3 to 4h of peanut butter ingestion, plasma C26:0 and C26:0/C22:0 were found to be significantly elevated to levels seen in patients with peroxisomal disorders. These levels returned to normal within 12h. Peanut consumption needs to be accounted for when interpreting VLCFAs.

Nutritional significance and metabolism of very long chain fatty alcohols and acids from dietary waxes

Very long chain fatty alcohols obtained from plant waxes and beeswax have been reported to lower plasma cholesterol in humans. This review discusses nutritional or regulatory effects produced by wax esters or aliphatic acids and alcohols found in unrefined cereal grains, beeswax, and many plant-derived foods. Reports suggest that 5-20 mg per day of mixed C24-C34 alcohols, including octacosanol and triacontanol, lower low-density lipoprotein (LDL) cholesterol by 21%-29% and raise high-density lipoprotein cholesterol by 8%-15%. Wax esters are hydrolyzed by a bile salt-dependent pancreatic carboxyl esterase, releasing long chain alcohols and fatty acids that are absorbed in the gastrointestinal tract. Studies of fatty alcohol metabolism in fibroblasts suggest that very long chain fatty alcohols, fatty aldehydes, and fatty acids are reversibly inter-converted in a fatty alcohol cycle. The metabolism of these compounds is impaired in several inherited human peroxisomal disorders, including adrenoleukodystrophy and Sjögren-Larsson syndrome. Reports on dietary management of these diseases confirm that very long chain fatty acids (VLCFA) are normal constituents of the human diet and are synthesized endogenously. Concentrations of VLCFA in blood plasma increase during fasting and when children are placed on ketogenic diets to suppress seizures. Existing data support the hypothesis that VLCFA exert regulatory roles in cholesterol metabolism in the peroxisome and also alter LDL uptake and metabolism.

Bleeding in a patient taking Lorenzo's oil: evidence for a vascular defect

We describe a man with adrenoleukodystrophy receiving Lorenzo's oil (glycerol trioleate and glycerol trierucate) who developed purpura, petechiae, and bleeding. Bleeding time was markedly increased (>20 min), although he had only borderline thrombocytopenia (120 x 10(9)/1) and conventional platelet aggregation studies were normal (except for a borderline response to low concentration collagen), as were results using a new technique employing immobilised von Willebrand factor. Together these results suggest that bleeding in this man resulted from a defect in vascular wall function or in the interaction of platelets with the endothelium.

Very long chain fatty acids in higher animals--a review

Fatty acids with greater than 22 carbon atoms (very long chain fatty acids, VLCFA) are present in small amounts in most animal tissues. Saturated and monoenoic VLCFA are major components of brain, while the polyenoic VLCFA occur in significant amounts in certain specialized animal tissues such as retina and spermatozoa. Biosynthesis of VLCFA occurs by carbon chain elongation of shorter chain fatty acid precursors while beta-oxidation takes place almost exclusively in peroxisomes. Mitochondria are unable to oxidize VLCFA because they lack a specific VLCFA coenzyme A synthetase, the first enzyme in the beta-oxidation pathway. VLCFA accumulate in the tissues of patients with inherited abnormalities in peroxisomal assembly, and also in individuals with defects in enzymes catalyzing individual reactions along the beta-oxidation pathway. It is believed that the accumulation of VLCFA in patient tissues contributes to the severe pathological changes which are a feature of these conditions. However, little is known of the role of VLCFA in normal cellular processes, and of the molecular basis for their contribution to the disease process. The present review provides an outline of the current knowledge of VLCFA including their biosynthesis, degradation, possible function and involvement in human disease.

Komrower Lecture. Adrenoleukodystrophy: natural history, treatment and outcome

Our laboratory has identified nearly 2000 patients with X-linked adrenoleukodystrophy (ALD) and conducted therapeutic trials in groups of patients who represent the major phenotypes. We report recent results of dietary therapy with a mixture of glyceryl trioleate and glyceryl trierucate oil, also referred to as Lorenzo's Oil, in the asymptomatic and childhood cerebral phenotypes. Fifty-three patients started this therapy at a mean age of 7.5 years at a time when they were free of neurological symptoms. Although analysis of data is hampered by the lack of a concurrent control group, follow-up studies after 39 months of therapy suggest that subsequent neurological involvement was less frequent and less severe than anticipated from historical controls. Retrospective analysis of the effect of the oil in patients with the severe childhood cerebral phenotype indicates that there was a slight but statistically significant slowing of clinical progression and delay of death.

Brain, liver, and adipose tissue erucic and very long chain fatty acid levels in adrenoleukodystrophy patients treated with glyceryl trierucate and trioleate oils (Lorenzo's oil)

Brain, liver, and adipose lipids were studied in the postmortem tissues of four adrenoleukodystrophy patients who had been treated with a mixture of glyceryl trioleate and trierucate oils ("Lorenzo's Oil") and compared to 7 untreated ALD patients and 3 controls. The dietary therapy appeared to reduce the levels of saturated very long chain fatty acids in the plasma, adipose tissue and liver; in the brain they were reduced in only one of the four patients. While substantial amounts of erucic acid were present in some of the tissues even 12 months after therapy had been discontinued, the levels in brain did not exceed those in controls at any time. The failure of erucic acid to enter the brain in significant quantity may be a factor in the disappointing results of dietary therapy for adrenoleukodystrophy.

Thrombocytopenia induced by erucic acid therapy in patients with X-linked adrenoleukodystrophy

Five patients with various clinical and genetic phenotypes of adrenoleukodystrophy were treated with a diet enriched with glycerol trioleate and glycerol trierucate (GTE). In all patients platelet counts decreased upon the administration of GTE, but no bleeding symptoms occurred in any of the patients, and bleeding time remained normal. Pseudothrombocytopenia was excluded in all patients. Thrombocytopenia was marked (84,000-37,000/mm) in three of the patients but was fully reversible after discontinuation of GTE. Mean platelet volumes were abnormally increased in all patients. When GTE was again administered by stepwise increasing the daily dose, platelet counts showed a clearly dose-dependent decrease. Bone marrow biopsies revealed no evidence of reduced megakaryocytopoiesis. The data indicate that in patients with adrenoleukodystrophy treated with GTE platelet counts should be closely monitored because thrombocytopenia may limit the maximal daily intake of GTE.

Effects of exogenous monounsaturated fatty acids on fatty acid metabolism in cultured skin fibroblasts from adrenoleukodystrophy patients

The conversion of [1-14C]16:0 to very-long-chain saturated fatty acids (VLCSFA) was greater in fibroblasts from adrenoleukodystrophy (ALD) patients than fibroblasts from normal subjects. Added 23:1(n-9) decreased the formation of VLCSFA from [1-14C]16:0 in ALD fibroblasts to the value found in normal fibroblasts. Chain-elongation as well as extensive chain-shortening of added 20:1(n-9), 22:1(n-9), 23:1(n-9) and 24:1(n-9) occurred in both normal and ALD fibroblasts, with chain-shortening being less in ALD than in normal fibroblasts. Added 18:1(n-9) together with 22:1(n-9) reduced the levels of both VLCSFA and total n-6 and n-3 polyunsaturated fatty acids (PUFA) in normal and ALD fibroblasts. The levels of total (n-6) and (n-3) PUFA but not the levels of VLCSFA were readily restored by culturing the cells in the presence of 18:1(n-9), 22:1(n-9), 18:2(n-6) and 18:3(n-3). The results are consistent with added monounsaturated fatty acids reducing levels of VLCSFA in ALD fibroblasts by depressing their biosynthesis from 16:0. They also support the use of oils rich in long chain monoenes as a dietary therapy for ALD patients but caution that the PUFA status of ALD patients should be monitored with a view to dietary supplementation, if necessary, with PUFA.

Adrenoleukodystrophy: phenotypic variability and implications for therapy

X-linked adrenoleukodystrophy (ALD) is a relatively common disorder that shows a great deal of phenotypic variability. Approximately half of the patients have the rapidly progressive childhood cerebral form that is associated with an inflammatory response in brain and leads to total disability or death during the first decade. Twenty five per cent or more of the patients have adrenomyeloneuropathy (AMN), a form that progresses slowly, involves the spinal cord mainly, shows little or no inflammatory response, manifests in adulthood, and is compatible with a near-normal life span. The two forms of the disease occur frequently within the same kindreds and nuclear families. Segregation analysis based on 3862 individuals in 89 kindreds points to the existence of an autosomal modifier locus with a likelihood ratio of 20:1. In addition, we present preliminary results of three types of therapy. Two hundred and four patients have received a dietary regimen that combines the administration of oils containing mono-unsaturated fatty acids (oleic and erucic) with the restricted intake of very long-chain fatty acids. This regimen normalizes the levels of satured very long-chain fatty acids in plasma within 4 weeks. It appears to improve peripheral nerve function in patients with AMN, and a large-scale trial is in progress to determine whether it can prevent the onset of neurological involvement in patients who have the biochemical abnormality of ALD but are neurologically intact. We report early results of bone marrow transplantation in 14 patients. There is encouraging but still preliminary evidence that transplantation can arrest the progression of the disease in patients with mild neurological involvement. There is urgent need to develop methods to combat the rapid progression of the cerebral forms of the disease, which so far has resisted therapeutic intervention, including immunosuppression or the administration of immunoglobulin.

Adrenomyeloneuropathy presenting as Addison's disease in childhood

Adrenoleukodystrophy, a sex-linked peroxisomal disorder that results in the impaired oxidation of long-chain saturated fatty acids and causes neurologic impairment, is a rare cause of Addison's disease in children. Adrenomyeloneuropathy is the name given to a biochemically identical but milder and more slowly progressive variant of adrenoleukodystrophy that affects young adults, in whom adrenal insufficiency may long precede nervous system dysfunction. The transmission of adrenomyeloneuropathy, like that of most cases of adrenoleukodystrophy, is sex-linked. Because of a preponderance of male patients among a group of patients with the onset of adrenal failure in childhood, we questioned whether this condition might be the initial manifestation of adrenomyeloneuropathy. We therefore measured the plasma concentrations of very-long-chain saturated fatty acids in eight patients with adrenal insufficiency; of these, five had elevated plasma hexacosanoic acid concentrations (range, 2.42 to 6.43 mumol per liter; mean normal level [+/- SD], 0.83 +/- 0.45), confirming the presence of adrenomyeloneuropathy. Magnetic resonance imaging showed clear evidence of brain involvement in all five patients. Reexploration of the family histories revealed additional missed cases. We conclude that the possibility of adrenomyeloneuropathy should be considered in any boy with Addison's disease.

Treatment of infantile phytanic acid storage disease: clinical, biochemical and ultrastructural findings in two children treated for 2 years

Two patients with infantile phytanic acid storage disease (infantile Refsum disease), one of whom showed the presence of morphologically normal peroxisomes in a liver biopsy, were treated with a low phytanic acid diet for more than 2 years and the effects of treatment on certain clinical, biochemical and ultrastructural parameters were examined. Both patients showed evidence of either an improvement or stabilisation in their clinical condition. Plasma phytanic acid levels decreased to near normal values in approximately 6 weeks after the introduction of the diet; plasma pipecolic acid also declined markedly but the decrease was not so rapid and its level remained abnormal. C26:C22 fatty acid ratios decreased very slowly and even after 2 years the values remained grossly abnormal. Despite the marked reduction of phytanic acid in the liver, there was an increase in the C26:C22 fatty acid ratios and this appeared to be paralleled by an increase in inclusion bodies. Our data suggest that some patients with the infantile form of Refsum disease may show some clinical benefit from dietary management and this is reflected biochemically by decreases in the plasma levels of phytanic acid and pipecolic acid.

Effects of long-chain, saturated fatty acids on membrane microviscosity and adrenocorticotropin responsiveness of human adrenocortical cells in vitro

Adrenoleukodystrophy (ALD) and adrenomyeloneuropathy are inherited disorders in which long-chain, saturated fatty acids (LCFA) accumulate in various tissues. A mechanism by which LCFA cause the endocrine and neurological dysfunction characteristic of these diseases is proposed based on in vitro response of human adrenocortical cells to ACTH in the presence of various fatty acids. Human adrenocortical cells cultured in the presence of 5 microM hexacosanoic (C26:0) or lignoceric (C24:0) acids showed decreased basal and ACTH-stimulated cortisol release compared with cells cultured without exogenous fatty acids or in the presence of linoleic acid (C18:2). Measurement of fluorescence polarization demonstrates a significant increase in the membrane microviscosity of cells cultured in the presence of LCFA. It is hypothesized that cells exposed to LCFA have increased membrane microviscosity with a consequent decrease in their ability to respond to ACTH. This decrease in trophic support may contribute to the adrenal insufficiency and atrophy in patients with ALD.

Peroxisomal disorders. A review of a recently recognized group of clinical entities

The peroxisome is a small organelle present in almost all cells. The peroxisomal disorders are a newly recognized group of disease entities that share structural and/or functional abnormalities of the peroxisomes, are inherited, and may have profound neurologic and systemic effects. Some of the disorders lack peroxisomes in cells, while others have single or multiple peroxisomal enzymatic deficiencies despite the presence of normally appearing peroxisomes. The prototype of the peroxisomal disorders is Zellweger syndrome. X-linked adrenoleukodystrophy, neonatal adrenoleukodystrophy, infantile Refsum disease, hyperpipecolic acidemia and Refsum disease are some of the other disease entities presently classified as peroxisomal disorders. Accurate methods of pre- and postnatal diagnosis are available. Treatment strategies are being developed, but at this time prenatal diagnosis and appropriate genetic counseling is the best therapeutic intervention for those peroxisomal disorders characterized by profound neurologic handicap and early death.

Adrenoleukodystrophy: from bedside to molecular biology

Although X-linked adrenoleukodystrophy was first described in 1923, the key advances in understanding the disorder followed discoveries beginning in 1973 that it was characterized by the tissue accumulation of very long chain fatty acids, particularly hexacosanoic acid (C26:0). Very long chain fatty acid assays in plasma, red cells, fibroblasts, or amniocytes permit prenatal and postnatal diagnosis and carrier detection. The phenotype of X-linked adrenoleukodystrophy is varied and ranges from the severe and fatal childhood form, to persons who remain asymptomatic in adult life. The underlying biochemical defect is the impaired capacity to degrade very long chain fatty acids, a reaction which normally takes place in the peroxisome. The locus of the adrenoleukodystrophy gene has been mapped to the terminal (Q28) segment of the long arm of the X-chromosome, in close proximity to the loci of Hemophilia A and red-green color blindness. A DNA probe (St14) for this portion of the X-chromosome is of aid for carrier detection. A new dietary regimen, which combines restricted very long chain fatty acid intake with the administration of a glycerol trioleate oil, is capable of reducing plasma very long chain fatty acid levels, and may offer neurological benefit.

Phenotype heterogeneity among hemizygotes in a family biochemically screened for adrenoleukodystrophy

We report on two clinically, neurologically normal relatives of a boy affected by adrenoleukodystrophy (ALD); they were found repeatedly to have the biochemical defect of an ALD hemizygote. The assay consisted in the determination of very-long-chain fatty acids in lyophilized and reconstituted plasma. While no evidence of neurologic disease (leukodystrophy or myeloneuropathy) was present in these hemizygotes, adrenocortical insufficiency provoking compensatory high ACTH release was found in both. These findings should be taken into consideration when counseling families in which cases with clinically expressed ALD are represented in several generations.

A new dietary therapy for adrenoleukodystrophy: biochemical and preliminary clinical results in 36 patients

A new dietary regimen has been administered for periods ranging from 60 days to 1 1/2 years in 34 patients with various forms of X-linked adrenoleukodystrophy (ALD), as well as in 1 patient with neonatal ALD and 1 patient with infantile Refsum's disease. The diet combines the administration of a glyceryl trioleate oil (GTO) with the dietary restriction of very-long-chain fatty acids (VLFA), particularly hexacosanoic acid (C26:0). Reductions in the levels of plasma C26:0 and other VLFA were achieved in 25 of the 36 patients. Fifteen of these 25 patients were treated for more than 100 days. The mean reduction of the plasma C26:0 level was 53% (range, 22 to 73%) in these 15 patients. While the focus of the study was on biochemical variables, comparison of pre- and post-diet studies of peripheral nerve function showed improvement in 1 patient with adrenomyeloneuropathy (AMN) and 1 heterozygote. In contrast, 2 patients with ALD onset in childhood developed new neurological deficits while on therapy. We conclude that it is possible to lower plasma VLFA levels in ALD patients. A clinical trial is indicated to test whether this approach can alter the neurological progression in patients with AMN or in symptomatic heterozygotes, and to determine whether it can prevent the onset of neurological disability in asymptomatic persons who have the biochemical defect of ALD.

Adrenoleukodystrophy: dietary oleic acid lowers hexacosanoate levels

Adrenoleukodystrophy (ALD) is an X-linked disorder characterized by demyelination, adrenal insufficiency, and accumulation of saturated very-long-chain fatty acids (VLFA), particularly hexacosanoate (C26:0). We treated 5 patients with adrenoleukodystrophy (3 males and 2 symptomatic female carriers) for 6 months with a diet enriched in oleic acid (C18:1) and moderately restricted in C26:0. Elevated plasma and erythrocyte levels of C26:0 decreased in a time-dependent manner during treatment. Total plasma C26:0 concentration was lowered by 50 +/- 9% (p less than 0.01); it became normal in the female carriers. The total erythrocyte level of C26:0 decreased (44 +/- 5%; p less than 0.001) into the normal range in all patients. Significant decreases were noted in the saturated VLFA composition of plasma and erythrocyte sphingomyelin and erythrocyte phosphatidylcholine during dietary treatment. In general, decreases in saturated VLFA levels were accompanied by increases in monounsaturated VLFA levels, while total VLFA values did not change. This novel approach to the treatment of adrenoleukodystrophy, in which there is an exchange of monounsaturated VLFA for the more toxic saturated VLFA, may prove clinically beneficial in this disorder.

Adrenoleukodystrophy: biochemical procedures in diagnosis, prevention and treatment

The childhood form of adrenoleukodystrophy is an X-linked recessive disorder which is characterized biochemically by elevated concentrations of saturated very long chain fatty acids in tissues and plasma and impaired very long chain fatty acid oxidation in fibroblasts and leukocytes from adrenoleukodystrophy patients. The most consistently observed increase is that in hexacosanoic acid (C26:0); thus, measurement of plasma C26:0 concentration by gas-liquid chromatography provides a rapid, sensitive method of diagnosis. Prenatal diagnosis of adrenoleukodystrophy can be made by measurement of C26:0 concentrations in amniocytes and chorionic villus cells. Heterozygote (carrier) detection has also been accomplished by biochemical measurement of C26:0 in plasma and skin fibroblasts. In a study of over 200 obligate heterozygotes, greater than 90% showed abnormal concentrations of C26:0. Hybridization studies using the cloned DNA fragment St14 detects polymorphisms in the distal end of the long arm of the X chromosome (Xq27-28) and six informative kindreds have shown co-segregation of adrenoleukodystrophy and the St14 marker through 65 meioses. Thus, such studies can supplement very long chain fatty acid concentrations in heterozygote detection. Therapeutic interventions for adrenoleukodystrophy, such as dietary restriction of very long chain fatty acids, administration of clofibrate or carnitine, immunosuppression and adrenal hormone replacement, have not been successful. Recently, a modification of the very long chain fatty acid-restricted diet has been employed in which this diet is supplemented with synthetic glycerol trioleate. The rationale for this diet is that decreased very long chain fatty acid synthesis by fibroblasts from patients with adrenoleukodystrophy was observed when oleic acid was added to the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenoleukodystrophy: survey of 303 cases: biochemistry, diagnosis, and therapy

Adrenoleukodystrophy (ALD) is a genetically determined disorder associated with progressive central demyelination and adrenal cortical insufficiency. All affected persons show increased levels of saturated unbranched very-long-chain fatty acids, particularly hexacosanoate (C26:0), because of impaired capacity to degrade these acids. This degradation normally takes place in a subcellular organelle called the peroxisome, and ALD, together with Zellweger's cerebrohepatorenal syndrome, is now considered to belong to the newly formed category of peroxisomal disorders. Biochemical assays permit prenatal diagnosis, as well as identification of most heterozygotes. We have identified 303 patients with ALD in 217 kindreds. These patients show a wide phenotypic variation. Sixty percent of patients had childhood ALD and 17% adrenomyeloneuropathy, both of which are X-linked, with the gene mapped to Xq28. Neonatal ALD, a distinct entity with autosomal recessive inheritance and points of resemblance to Zellweger's syndrome, accounted for 7% of the cases. Although excess C26:0 in the brain of patients with ALD is partially of dietary origin, dietary C26:0 restriction did not produce clear benefit. Bone marrow transplant lowered the plasma C26:0 level but failed to arrest neurological progression.