Adrenoleukodystrophy in Norway: high rate of de novo mutations and age-dependent penetrance

Phenotypic Characterization of Female Carrier Mice Heterozygous for Tafazzin Deletion

Barth syndrome (BTHS) is caused by mutations in tafazzin resulting in deficits in cardiolipin remodeling that alter major metabolic processes. The tafazzin gene is encoded on the X chromosome, and therefore BTHS primarily affects males. Female carriers are typically considered asymptomatic, but age-related changes have been reported in female carriers of other X-linked disorders. Therefore, we examined the phenotype of female mice heterozygous for deletion of the tafazzin gene (Taz-HET) at 3 and 12 months of age. Food intakes, body masses, lean tissue and adipose depot weights, daily activity levels, metabolic measures, and exercise capacity were assessed. Age-related changes in mice resulted in small but significant genotype-specific differences in Taz-HET mice compared with their female Wt littermates. By 12 months, Taz-HET mice weighed less than Wt controls and had smaller gonadal, retroperitoneal, and brown adipose depots and liver and brain masses, despite similar food consumption. Daily movement, respiratory exchange ratio, and total energy expenditure did not vary significantly between the age-matched genotypes. Taz-HET mice displayed improved glucose tolerance and insulin sensitivity at 12 months compared with their Wt littermates but had evidence of slightly reduced exercise capacity. Tafazzin mRNA levels were significantly reduced in the cardiac muscle of 12-month-old Taz-HET mice, which was associated with minor but significant alterations in the heart cardiolipin profile. This work is the first to report the characterization of a model of female carriers of heterozygous tafazzin deficiency and suggests that additional study, particularly with advancing age, is warranted.

Neurocognitive and mental health impact of adrenoleukodystrophy across the lifespan: Insights for the era of newborn screening

X-linked adrenoleukodystrophy (ALD) is a rare inherited neurological disorder that poses considerable challenges for clinical management throughout the lifespan. Although males are generally more severely affected than females, the time course and presentation of clinical symptoms are otherwise difficult to predict. Opportunities to improve outcomes for individuals with ALD are rapidly expanding due to the introduction of newborn screening programs for this condition and an evolving treatment landscape. The aim of this comprehensive review is to synthesize current knowledge regarding the neurocognitive and mental health effects of ALD. This review provides investigators and clinicians with context to improve case conceptualization, inform prognostic counseling, and optimize neuropsychological and mental health care for patients and their families. Results highlight key predictive factors and brain-behavior relationships associated with the diverse manifestations of ALD. The review also discusses considerations for endpoints within clinical trials and identifies gaps to address in future research.

Return of non-ACMG recommended incidental genetic findings to pediatric patients: considerations and opportunities from experiences in genomic sequencing

BACKGROUND

The uptake of exome/genome sequencing has introduced unexpected testing results (incidental findings) that have become a major challenge for both testing laboratories and providers. While the American College of Medical Genetics and Genomics has outlined guidelines for laboratory management of clinically actionable secondary findings, debate remains as to whether incidental findings should be returned to patients, especially those representing pediatric populations.

METHODS

The Sequencing Analysis and Diagnostic Yield working group in the Clinical Sequencing Evidence-Generating Research Consortium has collected a cohort of pediatric patients found to harbor a genomic sequencing-identified non-ACMG-recommended incidental finding. The incidental variants were not thought to be associated with the indication for testing and were disclosed to patients and families.

RESULTS

In total, 23 "non-ACMG-recommended incidental findings were identified in 21 pediatric patients included in the study. These findings span four different research studies/laboratories and demonstrate differences in incidental finding return rate across study sites. We summarize specific cases to highlight core considerations that surround identification and return of incidental findings (uncertainty of disease onset, disease severity, age of onset, clinical actionability, and personal utility), and suggest that interpretation of incidental findings in pediatric patients can be difficult given evolving phenotypes. Furthermore, return of incidental findings can benefit patients and providers, but do present challenges.

CONCLUSIONS

While there may be considerable benefit to return of incidental genetic findings, these findings can be burdensome to providers and present risk to patients. It is important that laboratories conducting genomic testing establish internal guidelines in anticipation of detection. Moreover, cross-laboratory guidelines may aid in reducing the potential for policy heterogeneity across laboratories as it relates to incidental finding detection and return. However, future discussion is required to determine whether cohesive guidelines or policy statements are warranted.

ABCD1 Gene Mutations: Mechanisms and Management of Adrenomyeloneuropathy

Pathogenic variants in the ABCD1 gene on the X chromosome may result in widely heterogenous phenotypes, including adrenomyeloneuropathy (AMN). Affected males typically present in their third or fourth decade of life with progressive lower limb weakness and spasticity, and may develop signs and symptoms of adrenal insufficiency and/or cerebral demyelination. Heterozygous females may be asymptomatic, but may develop a later-onset and more slowly progressive spastic paraparesis. In this review, we describe the clinical presentation of AMN, as well as its diagnosis and management. The role of rehabilitative therapies and options for management of spasticity are highlighted.

X‑linked adrenoleukodystrophy caused by maternal ABCD1 mutation and paternal X chromosome inactivation

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder. It is caused by defects in the ATP-binding cassette subfamily D member 1 (ABCD1) gene, resulting in impaired peroxisomal β-oxidation of very-long-chain fatty acids (VLCFAs). As an X-linked recessive disease, female X-ALD carriers are typically asymptomatic. In the present study, a 7-year-old girl was diagnosed with cerebral ALD. Brain magnetic resonance imaging revealed asymmetric demyelination of bilateral white matter. Plasma VLCFAs level showed a substantial increase. Whole exome and Sanger sequencing revealed an ABCD1 c.919C>T (p.Q307X) heterozygous pathogenic mutation, which was inherited from the asymptomatic mother. X chromosome inactivation (XCI) analysis revealed that the normal paternal X chromosome was almost completely inactivated. Thus, the maternal ABCD1 mutation and paternal XCI were responsible for causing the disease in the patient. XCI may be one reason female X-ALD carriers can be symptomatic.

A Large Family with p.Arg554His Mutation in ABCD1: Clinical Features and Genotype/Phenotype Correlation in Female Carriers

X-linked adrenoleukodystrophy (X-ALD, OMIM #300100) is the most common peroxisomal disorder clinically characterized by two main phenotypes: adrenomyeloneuropathy (AMN) and the cerebral demyelinating form of X-ALD (cerebral ALD). The disease is caused by defects in the gene for the adenosine triphosphate (ATP)-binding cassette protein, subfamily D (ABCD1) that encodes the peroxisomal transporter of very-long-chain fatty acids (VLCFAs). The defective function of ABCD1 protein prevents β-oxidation of VLCFAs, which thus accumulate in tissues and plasma, to represent the hallmark of the disease. As in many X-linked diseases, it has been routinely expected that female carriers are asymptomatic. Nonetheless, recent findings indicate that most ABCD1 female carriers become symptomatic, with a motor disability that typically appears between the fourth and fifth decade. In this paper, we report a large family in which affected males died during the first decade, while affected females develop, during the fourth decade, progressive lower limb weakness with spastic or ataxic-spastic gait, tetra-hyperreflexia with sensory alterations. Clinical and genetic evaluations were performed in nine subjects, eight females (five affected and three healthy) and one healthy male. All affected females were carriers of the c.1661G>A (p.Arg554His, rs201568579) mutation. This study strengthens the relevance of clinical symptoms in female carriers of ABCD1 mutations, which leads to a better understanding of the role of the genetic background and the genotype-phenotype correlation. This indicates the relevance to include ABCD1 genes in genetic panels for gait disturbance in women.

ABCD1 gene mutation in an Italian family with X-linkedadrenoleukodystrophy: case series

SUMMARY

Adrenoleukodystrophy is a peroxisomal X-linked recessive disease caused by mutations in the ABCD1 gene, located on the X-chromosome (Xq28). Gene mutations in patient with adrenoleukodystrophy induce metabolic alterations characterized by impaired peroxisomal beta-oxidation and accumulation of very long chain fatty acid (VLCFA) in plasma and in all tissues. Although nutritional intervention associated with a various mixture of oil prevents the accumulation of VLCFA, to date no causal treatment is available. Therefore, haematopoietic stem cell transplantation (HSCT) and gene therapy are allowed only for very early stages of cerebral forms diagnosed during childhood.We reported a case series describing five family members affected by X-linked adrenoleukodystrophy caused by a novel mutation of the ABCD1 gene. Particularly, three brothers were affected while the sister and mother carried the mutation of the ABCD1 gene. In this family, the disease was diagnosed at different ages and with different clinical pictures highlighting the wide range of phenotypes related to this novel mutation. In addition, these characteristics stress the relevant role of early diagnosis to properly set a patient-based follow-up.

LEARNING POINTS

We report a novel mutation in the ABCD1 gene documented in a family group associated to an X-ALD possible Addison only phenotype. All patients present just Addison disease but with different phenotypes despite the presence of the same mutations. Further follow-up is necessary to complete discuss the clinical development. The diagnosis of ALD needs to be included in the differential diagnosis in all patients with idiopathic PAI through accurate evaluation of VLCFA concentrations and genetic confirmation testing. Early diagnosis of neurological manifestation is important in order to refer timely to HSCT. Further follow-up of these family members is necessary to characterize the final phenotype associated with this new mutation.

Newborn Screening for X-Linked Adrenoleukodystrophy in Georgia: Experiences from a Pilot Study Screening of 51,081 Newborns

We screened 51,081 newborns for X-linked adrenoleukodystrophy (ALD) using a two-tiered strategy quantifying very long chain lysophosphatadylcholines (LPC). Our testing strategy used flow injection tandem mass spectrometry for the first-tier analysis of LPCs, and second-tier quantification of C26:0 LPC using liquid chromatography tandem mass spectrometry. There were 364 specimens considered abnormal using our first-tier algorithm that relied on the four LPC measurements and post-analytical tools. Second-tier test results were reported as normal or abnormal based on a cutoff for the single analyte, C26:0 LPC. Eleven cases were reported as abnormal based on second-tier test results. One male with ALD was identified, and two females with peroxisomal biogenesis disorders were also identified. A single female case remains unresolved, due to a loss to follow up after a negative molecular test result for ABCD1 gene sequencing. The positive predictive value for confirmed, clinically relevant disorders during this pilot study was 27.3%. Challenges identified during the study period were based around coverage for confirmatory testing, particularly if family members needed molecular testing, which is an ongoing issue with newborn screening in Georgia. We also encountered issues with the follow up for a patient who remained asymptomatic. Due to the different timelines involved with clinical findings in ALD, follow-up coordination may be more difficult, particularly if the child identified by newborn screening (NBS) is the only member of the family affected, or able to be tested.

The Changing Face of Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is a rare X-linked disorder of peroxisomal oxidation due to mutations in ABCD1. It is a progressive condition with a variable clinical spectrum that includes primary adrenal insufficiency, myelopathy, and cerebral ALD. Adrenal insufficiency affects over 80% of ALD patients. Cerebral ALD affects one-third of boys under the age of 12 and progresses to total disability and death without treatment. Hematopoietic stem cell transplantation (HSCT) remains the only disease-modifying therapy if completed in the early stages of cerebral ALD, but it does not affect the course of adrenal insufficiency. It has significant associated morbidity and mortality. A recent gene therapy clinical trial for ALD reported short-term MRI and neurological outcomes comparable to historical patients treated with HSCT without the associated adverse side effects. In addition, over a dozen states have started newborn screening (NBS) for ALD, with the number of states expecting to double in 2020. Genetic testing of NBS-positive neonates has identified novel variants of unknown significance, providing further opportunity for genetic characterization but also uncertainty in the monitoring and therapy of subclinical and/or mild adrenal insufficiency or cerebral involvement. As more individuals with ALD are identified at birth, it remains uncertain if availability of matched donors, transplant (and, potentially, gene therapy) centers, and specialists may affect the timely treatment of these individuals. As these promising gene therapy trials and NBS transform the clinical management and outcomes of ALD, there will be an increasing need for the endocrine management of presymptomatic and subclinical adrenal insufficiency. (Endocrine Reviews 41: 1 - 17, 2020).

Adrenoleukodystrophy in the era of newborn screening

PURPOSE OF REVIEW

Adrenoleukodystrophy (ALD) is a peroxisomal disorder with varying clinical presentations, including adrenal insufficiency, neurologic disease, and testicular dysfunction. The present review is intended to describe the current knowledge of the pathophysiology of ALD and provide an update regarding newborn screening, diagnosis, monitoring, and treatment.

RECENT FINDINGS

New York State initiated newborn screening for ALD on December 30, 2013. Successful ALD newborn screening has led to its addition on other state newborn screens and recommendations for universal screening. Initial incidence reports, based on newborn screening, suggest ALD may be more common than previously described. The Pediatric Endocrine Society has published guidance for monitoring newborn males with ALD and case reports suggest biochemical adrenal insufficiency can be present during early infancy. Allogeneic hematopoietic stem cell transplant and gene therapy have been effective at halting the progression of cerebral ALD.

SUMMARY

Early diagnosis and monitoring for progression of ALD can prevent adrenal crisis and treat the cerebral form of the disease. Initial guidelines for surveillance are likely to evolve as newborn screening not only aids in early detection and therapeutic interventions for ALD, but also expands our knowledge of the natural history of ALD.

Epidemiology, pathogenesis, and diagnosis of Addison's disease in adults

BACKGROUND

Addison's disease (AD) is a rare disorder and among adult population in developed countries is most commonly caused by autoimmunity. In contrast, in children genetic causes are responsible for AD in the majority of patients.

PURPOSE

This review describes epidemiology, pathogenesis, genetics, natural history, clinical manifestations, immunological markers and diagnostic strategies in patients with AD. Standard care treatments including the management of patients during pregnancy and adrenal crises consistent with the recent consensus statement of the European Consortium and the Endocrine Society Clinical Practice Guideline are described. In addition, emerging therapies designed to improve the quality of life and new strategies to modify the natural history of autoimmune AD are discussed.

CONCLUSIONS

Progress in optimizing replacement therapy for patients with AD has allowed the patients to lead a normal life. However, continuous education of patients and health care professionals of ever-present danger of adrenal crisis is essential to save lives of patients with AD.

The many faces of peroxisomal disorders: Lessons from a large Arab cohort

Defects in the peroxisomes biogenesis and/or function result in peroxisomal disorders. In this study, we describe the largest Arab cohort to date (72 families) of clinically, biochemically and molecularly characterized patients with peroxisomal disorders. At the molecular level, we identified 43 disease-causing variants, half of which are novel. The founder nature of many of the variants allowed us to calculate the minimum disease burden for these disorders in our population ~1:30 000, which is much higher than previous estimates in other populations. Clinically, we found an interesting trend toward genotype/phenotype correlation in terms of long-term survival. Nearly half (40/75) of our peroxisomal disorders patients had documented survival beyond 1 year of age. Most unusual among the long-term survivors was a multiplex family in which the affected members presented as adults with non-specific intellectual disability and epilepsy. Other unusual presentations included the very recently described peroxisomal fatty acyl-CoA reductase 1 disorder as well as CRD, spastic paraparesis, white matter (CRSPW) syndrome. We conclude that peroxisomal disorders are highly heterogeneous in their clinical presentation. Our data also confirm the demonstration that milder forms of Zellweger spectrum disorders cannot be ruled out by the "gold standard" very long chain fatty acids assay, which highlights the value of a genomics-first approach in these cases.

Natural history of a cohort of ABCD1 variant female carriers

BACKGROUND AND PURPOSE

The therapeutic scenario of X-linked adrenoleukodystrophy (X-ALD) is rapidly changing. Whereas the disease is well characterized in men, the condition remains to be fully clarified in women carrying ATP binding cassette subfamily D member 1 (ABCD1) variants. Specifically, data on clinical progression are needed, in order to recommend any appropriate management. The objective of this study was to outline the natural history of a cohort of untreated ABCD1 heterozygous female carriers.

METHODS

Longitudinal data from a single-center population of 60 carriers were retrospectively reviewed. Demographics, anthropometrics, serum very long chain fatty acid (VLCFA) levels, clinical parameters and the Adult ALD Clinical Score (AACS) were collected from every recorded visit in a 7-year period and analyzed to define the phenotype modifications, to determine factors associated with clinical features, and to estimate the annual progression rate and the subsequent sample size for interventional trials.

RESULTS

Thirty-two patients were eligible for the study, and 59.4% were symptomatic at baseline. Clinical severity worsens with age which increases risk of symptom onset, the cut-off of 41 years being crucial for phenoconversion. VLCFA levels were not predictive and did not change over time. Symptomatic carriers were followed up for 3.45 ± 2.1 years. The AACS increased at an annual rate of 0.24 points. The estimated sample size for 30% reduction in annual progression at 80% power was 272.

CONCLUSIONS

This study provides data on the natural disease progression of untreated ABCD1 heterozygous female carriers, demonstrating the relevance of aging. The estimated annual increase of the AACS will be useful for future interventional studies.

Association of Diagnosis of Leukodystrophy With Race and Ethnicity Among Pediatric and Adolescent Patients

IMPORTANCE

Inherited leukodystrophies are a group of neurological diseases affecting myelin that cause significant morbidities and death. Timely and correct diagnosis is important for initiating treatment, designing disease screening, and offering care and guidance to patients and families.

OBJECTIVE

To determine whether there are disparities in leukodystrophy diagnosis in different racial backgrounds.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study involved a retrospective review of patients aged 18 years or younger who were diagnosed with 1 of 4 leukodystrophies (metachromatic leukodystrophy, X-linked adrenoleukodystrophy, Krabbe disease, and Hurler disease) in the US Children's Hospital Association's Pediatric Health Information System database from October 1, 2015, through September 30, 2017.

MAIN OUTCOMES AND MEASURES

Leukodystrophy diagnosis and racial background of the patients were analyzed. Adjusted prevalence estimates of leukodystrophies were obtained by controlling for sex, insurance type, urban or rural status, 2010 median household income for patient zip code, number of inpatient days, and age at first visit. Pathogenic leukodystrophy gene allele frequencies in different racial backgrounds for ABCD1, ARSA, GALC, and IDUA were determined using the gnomAD database.

RESULTS

Of the 557 patients identified with a leukodystrophy (221 [40%] female; 321 [58%] white non-Hispanic, 54 [10%] black non-Hispanic, and 51 [9%] white Hispanic; median [range] age, 7 [0-18] years), nonwhite race, including black non-Hispanic, black Hispanic, and white Hispanic, was associated with not having a leukodystrophy diagnosis. The adjusted prevalence for a leukodystrophy diagnosis in white non-Hispanic patients was 13.8 (95% CI, 10.6-17.9) per 100 000 patients, compared with 5.8 (95% CI, 3.8-8.9), 2.4 (95% CI, 1.1-5.2), and 7.4 (95% CI, 5.2-10.4) per 100 000 in black non-Hispanic, black Hispanic, and white Hispanic patients, respectively. This reduced rate of diagnosis was out of proportion to the frequency of the different races in the Pediatric Health Information System database. Similar or higher frequencies of missense or loss-of-function alleles were measured in populations of Latino and African descent for the pathogenic leukodystrophy gene alleles. For example, for ABCD1, allele frequencies in those of Latino or African descent were 2.1 × 10-5 and 2.2 × 10-5, as compared with 1.4 × 10-5 for those of European non-Finnish descent.

CONCLUSIONS AND RELEVANCE

Patients of racial/ethnic minorities, including those from black, black Hispanic, and white Hispanic backgrounds, were significantly less likely to be diagnosed with a leukodystrophy. Leukodystrophy disease-associated allele frequencies were the same or higher in populations of Latino or African descent, arguing against a genetic founder effect being responsible for the lower diagnosis rates. This underdiagnosis has implications for newborn screening programs and treatment access and may reflect a more widespread problem in pediatric neurological and orphan diseases.

Economic impact of screening for X-linked Adrenoleukodystrophy within a newborn blood spot screening programme

BACKGROUND

A decision tree model was built to estimate the economic impact of introducing screening for X-linked adrenoleukodystrophy (X-ALD) into an existing tandem mass spectrometry based newborn screening programme. The model was based upon the UK National Health Service (NHS) Newborn Blood Spot Screening Programme and a public service perspective was used with a lifetime horizon. The model structure and parameterisation were based upon literature reviews and expert clinical judgment. Outcomes included health, social care and education costs and quality adjusted life years (QALYs). The model assessed screening of boys only and evaluated the impact of improved outcomes from hematopoietic stem cell transplantation in patients with cerebral childhood X-ALD (CCALD). Threshold analyses were used to examine the potential impact of utility decrements for non-CCALD patients identified by screening.

RESULTS

It is estimated that screening 780,000 newborns annually will identify 18 (95%CI 12, 27) boys with X-ALD, of whom 10 (95% CI 6, 15) will develop CCALD. It is estimated that screening may detect 7 (95% CI 3, 12) children with other peroxisomal disorders who may also have arisen symptomatically. If results for girls are returned an additional 17 (95% CI 12, 25) cases of X-ALD will be identified. The programme is estimated to cost an additional £402,000 (95% CI £399-407,000) with savings in lifetime health, social care and education costs leading to an overall discounted cost saving of £3.04 (95% CI £5.69, £1.19) million per year. Patients with CCALD are estimated to gain 8.5 discounted QALYs each giving an overall programme benefit of 82 (95% CI 43, 139) QALYs.

CONCLUSION

Including screening of boys for X-ALD into an existing tandem mass spectrometry based newborn screening programme is projected to reduce lifetime costs and improve outcomes for those with CCALD. The potential disbenefit to those identified with non-CCALD conditions would need to be substantial in order to outweigh the benefit to those with CCALD. Further evidence is required on the potential QALY impact of early diagnosis both for non-CCALD X-ALD and other peroxisomal disorders. The favourable economic results are driven by estimated reductions in the social care and education costs.

Adrenoleukodystrophy - neuroendocrine pathogenesis and redefinition of natural history

X-Linked adrenoleukodystrophy (ALD) is a peroxisomal metabolic disorder with a highly complex clinical presentation. ALD is caused by mutations in the ABCD1 gene, which leads to the accumulation of very long-chain fatty acids in plasma and tissues. Virtually all men with ALD develop adrenal insufficiency and myelopathy. Approximately 60% of men develop progressive cerebral white matter lesions (known as cerebral ALD). However, one cannot identify these individuals until the early changes are seen using brain imaging. Women with ALD also develop myelopathy, but generally at a later age than men and adrenal insufficiency or cerebral ALD are very rare. Owing to the multisystem symptomatology of the disease, patients can be assessed by the paediatrician, general practitioner, endocrinologist or a neurologist. This Review describes current knowledge on the clinical presentation, diagnosis and treatment of ALD, and highlights gaps in our knowledge of the natural history of the disease owing to an absence of large-scale prospective cohort studies. Such studies are necessary for the identification of new prognostic biomarkers to improve care for patients with ALD, which is particularly relevant now that newborn screening for ALD is being introduced.

CYP4F2 affects phenotypic outcome in adrenoleukodystrophy by modulating the clearance of very long-chain fatty acids

X-linked adrenoleukodystrophy (ALD) is a severe neurodegenerative disorder caused by the accumulation of very long-chain fatty acids (VLCFA) due to mutations in the ABCD1 gene. The phenotypic spectrum ranges from a fatal cerebral demyelinating disease in childhood (cerebral ALD) to a progressive myelopathy without cerebral involvement in adulthood (adrenomyeloneuropathy). Because ABCD1 mutations have no predictive value with respect to clinical outcome a role for modifier genes was postulated. We report that the CYP4F2 polymorphism rs2108622 increases the risk of developing cerebral ALD in Caucasian patients. The rs2108622 polymorphism (c.1297G>A) results in an amino acid substitution valine for methionine at position 433 (p.V433M). Using cellular models of VLCFA accumulation, we show that p.V433M decreases the conversion of VLCFA into very long-chain dicarboxylic acids by ω-oxidation, a potential escape route for the deficient peroxisomal β-oxidation of VLCFA in ALD. Although p.V433M does not affect the catalytic activity of CYP4F2 it reduces CYP4F2 protein levels markedly. These findings open perspectives for therapeutic interventions in a disease with currently limited treatment options.

Mild phenotype in an adult male with X-linked adrenoleukodystrophy - case report

X‐linked adrenoleukodystrophy may present with a deceptively mild phenotype, even in adult males. Tight collaboration between clinicians, geneticists, biochemists, and other specialists is increasingly required for clarification of diagnosis in cases with atypical presentation.

Progression rate of myelopathy in X-linked adrenoleukodystrophy heterozygotes

X-linked adrenoleukodystrophy heterozygote women can present adult onset myeloneuropathy and little is known about its natural history. We aimed to describe the progression rate of the neurological impairment in the prospective follow-up of our cohort and to look for prognostic factors. The neurological scales Japanese Orthopaedic Association (JOA) and Severity Score System for Progressive Myelopathy (SSPROM) were applied at baseline in 29 symptomatic carriers and in follow-up visits. Age at onset, disease duration, X inactivation pattern, determination of the allele expressed, plasma levels of the very long chain fatty acids and of the neuron-specific enolase, and somato-sensory evoked potentials, were taken at baseline. The slope of the linear regression of both JOA and SSPROM versus disease duration since the first symptom was estimated using mixed modeling. JOA and SSPROM decreased 0.42 and 1.87 points per year, respectively (p < 0.001). None of the parameters under study influenced these rates. We estimated that the number of carriers per arm needed in a future 12 month trial with 80% power and a 50% reduction in disease progression would be 225 women for JOA and 750 for SSPROM. The progression rates of the studied neurological scales were small, did not depend on any modifier factor known, and reflected the characteristically slow worsening of symptoms in X-ALD heterozygotes. Better biomarkers are still necessary for future studies.

The genetic landscape of X-linked adrenoleukodystrophy: inheritance, mutations, modifier genes, and diagnosis

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene encoding a peroxisomal ABC transporter. In this review, we compare estimates of incidence derived from different populations in order to provide an overview of the worldwide incidence of X-ALD. X-ALD presents with heterogeneous phenotypes ranging from adrenomyeloneuropathy (AMN) to inflammatory demyelinating cerebral ALD (CALD). A large number of different mutations has been described, providing a unique opportunity for analysis of functional domains within ABC transporters. Yet the molecular basis for the heterogeneity of clinical symptoms is still largely unresolved, as no correlation between genotype and phenotype exists in X-ALD. Beyond ABCD1, environmental triggers and other genetic factors have been suggested as modifiers of the disease course. Here, we summarize the findings of numerous reports that aimed at identifying modifier genes in X-ALD and discuss potential problems and future approaches to address this issue. Different options for prenatal diagnosis are summarized, and potential pitfalls when applying next-generation sequencing approaches are discussed. Recently, the measurement of very long-chain fatty acids in lysophosphatidylcholine for the identification of peroxisomal disorders was included in newborn screening programs.

Protective effect of antioxidants on DNA damage in leukocytes from X-linked adrenoleukodystrophy patients

Toxic metabolites accumulation and oxidative stress have been associated to the pathophysiology of X-linked adrenoleukodystrophy (X-ALD), an inborn error of peroxisome metabolism. Parameters of oxidative damage to proteins and lipids in X-ALD patients were already described in literature; however, DNA injuries were not studied yet. Considering that, the aims were to investigate DNA damage by comet assay in heterozygotes and symptomatic X-ALD patients, to look for associations between DNA damage and lipid peroxidation as measured by urinary 15-F2t-isoprostane; and to evaluate the in vitro effect of N-acetyl-l-cysteine (NAC), trolox (TRO) and rosuvastatin (RSV) on DNA damage in leukocytes from symptomatic patients. Symptomatic patients presented higher DNA damage levels than those found in heterozygotes and controls; heterozygotes and controls showed similar results. In order to investigate the in vitro antioxidant effect on DNA damage, whole blood cells from symptomatic patients were incubated with NAC (1 and 2.5mM), TRO (25 and 75 μM) and RSV (0.5, 2 and 5 μM) before DNA damage analysis. NAC, TRO and RSV, at all tested concentrations, were all capable to reduce DNA damage in symptomatic X-ALD patients until control levels. Finally, DNA damage correlated with urinary isoprostanes and plasmatic levels of TBA-RS and DCFH-DA, allowing to hypothesize that DNA damage might be induced by lipid peroxidation in symptomatic patients. The present work yields experimental evidence that NAC, TRO and RSV reduce the in vitro DNA injury in symptomatic X-ALD patients, what may suggest that the administration of these antioxidants might be considered as an adjuvant therapy for X-ALD.

Streamlined determination of lysophosphatidylcholines in dried blood spots for newborn screening of X-linked adrenoleukodystrophy

BACKGROUND

Pre-symptomatic hematopoietic stem cell transplantation is essential to achieve best possible outcomes for patients with the childhood cerebral form of X-linked adrenoleukodystrophy (X-ALD). We describe a high-throughput method for measurement of C20-C26 lysophosphatidylcholines (LPCs) and biochemical diagnosis of X-ALD using the same dried blood spots (DBS) routinely used for newborn screening.

METHODS

LPCs are extracted from 3-mm DBS punch with methanol containing an isotopically labeled LPC as internal standard. This extract is transferred to a 96-well plate, evaporated and then reconstituted in mobile phase for flow injection analysis tandem mass spectrometry (FIA-MS/MS) in selected reaction monitoring mode for measurement of four different LPCs (C20, C22, C24, C26) and the internal standard (d4-C26-LPC). Analysis time is 1.5min per sample.

RESULTS

The mean CVs from the intra- and inter-assay experiments for LPCs were 6.3-15.1% for C20-LPC, 4.4-18.6% for C22-LPC and 4.5-14.3% for C24-LPC. Limits of detection were determined for C20-LPC (LOD=0.03μg/mL), C22-LPC (0.03μg/mL), C24-LPC (0.03μg/mL) and C26-LPC (0.01μg/mL). Reference ranges were established from DBS of 130 newborns and 20 adults. Samples of patients with X-ALD (n=16), peroxisomal biogenesis disorders (n=8), and X-ALD carriers (n=12) were analyzed blindly and all were correctly identified.

CONCLUSION

Analysis of LPC species by FIA-MS/MS is a fast, simple and reliable method to screen for X-ALD and other peroxisomal disorders in DBS. To maximize specificity, abnormal results can be verified by a 2nd tier assay using LC-MS/MS.

Molecular analysis in X-linked adrenoleukodystrophy patients: identification of a novel mutation

X linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disease characterized by progressive demyelination of the central nervous system, adrenocortical insufficiency and elevated levels of very long chain fatty acids (VLCFAs). It is caused by mutations in ABCD1 gene located at Xq28. More than 1,300 mutations have been identified to date which is unique to each patient. In this study we report the mutational analysis of 2 X-ALD patients (1 male and 1 female) showing variable clinical spectrum. The mutation analysis of the female patient revealed IVS5-6delC (c.1489-6delC) and p. P543L variations in compound heterozygous state. The male patient was found to be hemizygous for a novel mutation, p. R104P. In conclusion, while defining a novel mutation, the cases presented herein may contribute to the mutation and clinical spectrum of X-ALD.