Progression of myelopathy in males with adrenoleukodystrophy: towards clinical trial readiness

Lipidomic biomarkers in plasma correlate with disease severity in adrenoleukodystrophy

BACKGROUND

X-linked adrenoleukodystrophy (ALD) is a neurometabolic disorder caused by pathogenic variants in ABCD1 resulting very long-chain fatty acids (VLCFA) accumulation in plasma and tissues. Males can present with various clinical manifestations, including adrenal insufficiency, spinal cord disease, and leukodystrophy. Female patients typically develop spinal cord disease and peripheral neuropathy. Predicting the clinical outcome of an individual patient remains impossible due to the lack of genotype-phenotype correlation and predictive biomarkers.

METHODS

The availability of a large prospective cohort of well-characterized patients and associated biobank samples allowed us to investigate the relationship between lipidome and disease severity in ALD. We performed a lipidomic analysis of plasma samples from 24 healthy controls, 92 male and 65 female ALD patients.

RESULTS

Here we show that VLCFA are incorporated into different lipid classes, including lysophosphatidylcholines, phosphatidylcholines, triglycerides, and sphingomyelins. Our results show a strong association between higher levels of VLCFA-containing lipids and the presence of leukodystrophy, adrenal insufficiency, and severe spinal cord disease in male ALD patients. In female ALD patients, VLCFA-lipid levels correlate with X-inactivation patterns in blood mononuclear cells, and higher levels are associated with more severe disease manifestations. Finally, hematopoietic stem cell transplantation significantly reduces, but does not normalize, plasma C26:0-lysophosphatidylcholine levels in male ALD patients. Our findings are supported by the concordance of C26:0-lysophosphatidylcholine and total VLCFA analysis with the lipidomics results.

CONCLUSIONS

This study reveals the profound impact of ALD on the lipidome and provides potential biomarkers for predicting clinical outcomes in ALD patients.

Four-dimensional lipidomics profiling in X-linked adrenoleukodystrophy using trapped ion mobility mass spectrometry

Lipids play pivotal roles in an extensive range of metabolic and physiological processes. In recent years, the convergence of trapped ion mobility spectrometry and MS has enabled 4D-lipidomics, a highly promising technology for comprehensive lipid analysis. 4D-lipidomics assesses lipid annotations across four distinct dimensions-retention time, collisional cross section, m/z (mass-to-charge ratio), and MS/MS spectra-providing a heightened level of confidence in lipid annotation. These advantages prove particularly valuable when investigating complex disorders involving lipid metabolism, such as adrenoleukodystrophy (ALD). ALD is characterized by the accumulation of very-long-chain fatty acids (VLCFAs) due to pathogenic variants in the ABCD1 gene. A comprehensive 4D-lipidomics strategy of ALD fibroblasts demonstrated significant elevations of various lipids from multiple classes. This indicates that the changes observed in ALD are not confined to a single lipid class and likely impacts a broad spectrum of lipid-mediated physiological processes. Our findings highlight the incorporation of mainly saturated and monounsaturated VLCFA variants into a range of lipid classes, encompassing phosphatidylcholines, triacylglycerols, and cholesterol esters. These include ultra-long-chain fatty acids with a length of up to thirty carbon atoms. Lipid species containing C26:0 and C26:1 were the most frequently detected VLCFA lipids in our study. Furthermore, we report a panel of 121 new candidate biomarkers in fibroblasts, exhibiting significant differentiation between controls and individuals with ALD. In summary, this study demonstrates the capabilities of a 4D-lipid profiling workflow in unraveling novel insights into the intricate lipid modifications associated with metabolic disorders like ALD.

International validation of meaningfulness of postural sway and gait to assess myeloneuropathy in adults with adrenoleukodystrophy

BACKGROUND

The most common manifestation of X-linked adrenoleukodystrophy (ALD) is a slowly progressive myeloneuropathy, which leads to imbalance and gait disturbances. The variable progression of the disease complicates evaluation of its progression rate. Wearable sensors allow for easy and frequent balance and gait collection. This study reports baseline data from a longitudinal study on the quantitative assessment of balance and gait with wearable sensors and their clinical relevance.

METHODS

Data were collected from adult patients in two institutions. Postural body sway and gait parameters were measured using accelerometers. Disease severity was measured by the Expanded Disability Severity Scale (EDSS). Falling frequency and quality of life (QOL) were collected in men. The relationship between sway and gait variables and EDSS score, participants' use of a walking aid, and falling frequency was evaluated.

RESULTS

One hundred twenty individuals with ALD were included. Sway variables significantly differentiate participants' assistive device use. Sway and gait variables were correlated to the EDSS in both sexes. Both gait speed and sway were correlated with falling frequency in men from one institution. Select QOL subscores were correlated with the EDSS in males from one institution. Accelerometry generated comparable results across sites.

DISCUSSION

This study confirms the clinical correlation between spinal cord disease and imbalance and gait in ALD. For the first time, this study shows clinically meaningful relationships for sway and gait with use of an assistive device, falling frequency and QOL. Wearable accelerometers are a valid means to measure sway and gait in ALD. These measures are promising outcomes for clinical trial designs to assess myeloneuropathy in ALD and to monitor disease progression in individuals.

Safety and efficacy of leriglitazone for preventing disease progression in men with adrenomyeloneuropathy (ADVANCE): a randomised, double-blind, multi-centre, placebo-controlled phase 2-3 trial

BACKGROUND

Adult patients with adrenoleukodystrophy have a poor prognosis owing to development of adrenomyeloneuropathy. Additionally, a large proportion of patients with adrenomyeloneuropathy develop life-threatening progressive cerebral adrenoleukodystrophy. Leriglitazone is a novel selective peroxisome proliferator-activated receptor gamma agonist that regulates expression of key genes that contribute to neuroinflammatory and neurodegenerative processes implicated in adrenoleukodystrophy disease progression. We aimed to assess the effect of leriglitazone on clinical, imaging, and biochemical markers of disease progression in adults with adrenomyeloneuropathy.

METHODS

ADVANCE was a 96-week, randomised, double-blind, placebo-controlled, phase 2-3 trial done at ten hospitals in France, Germany, Hungary, Italy, the Netherlands, Spain, the UK, and the USA. Ambulatory men aged 18-65 years with adrenomyeloneuropathy without gadolinium enhancing lesions suggestive of progressive cerebral adrenoleukodystrophy were randomly assigned (2:1 without stratification) to receive daily oral suspensions of leriglitazone (150 mg starting dose; between baseline and week 12, doses were increased or decreased to achieve plasma concentrations of 200 μg·h/mL [SD 20%]) or placebo by means of an interactive response system and a computer-generated sequence. Investigators and patients were masked to group assignment. The primary efficacy endpoint was change from baseline in the Six-Minute Walk Test distance at week 96, analysed in the full-analysis set by means of a mixed model for repeated measures with restricted maximum likelihood and baseline value as a covariate. Adverse events were also assessed in the full-analysis set. This study was registered with ClinicalTrials.gov, NCT03231878; the primary study is complete; patients had the option to continue treatment in an open-label extension, which is ongoing.

FINDINGS

Between Dec 8, 2017, and Oct 16, 2018, of 136 patients screened, 116 were randomly assigned; 62 [81%] of 77 patients receiving leriglitazone and 34 [87%] of 39 receiving placebo completed treatment. There was no between-group difference in the primary endpoint (mean [SD] change from baseline leriglitazone: -27·7 [41·4] m; placebo: -30·3 [60·5] m; least-squares mean difference -1·2 m; 95% CI -22·6 to 20·2; p=0·91). The most common treatment emergent adverse events in both the leriglitazone and placebo groups were weight gain (54 [70%] of 77 vs nine [23%] of 39 patients, respectively) and peripheral oedema (49 [64%] of 77 vs seven [18%] of 39). There were no deaths. Serious treatment-emergent adverse events occurred in 14 (18%) of 77 patients receiving leriglitazone and ten (26%) of 39 patients receiving placebo. The most common serious treatment emergent adverse event, clinically progressive cerebral adrenoleukodystrophy, occurred in six [5%] of 116 patients, all of whom were in the placebo group.

INTERPRETATION

The primary endpoint was not met, but leriglitazone was generally well tolerated and rates of adverse events were in line with the expected safety profile for this drug class. The finding that cerebral adrenoleukodystrophy, a life-threatening event for patients with adrenomyeloneuropathy, occurred only in patients in the placebo group supports further investigation of whether leriglitazone might slow the progression of cerebral adrenoleukodystrophy.

FUNDING

Minoryx Therapeutics.

Sex-specific newborn screening for X-linked adrenoleukodystrophy

Males with X-linked adrenoleukodystrophy (ALD) are at high risk for developing adrenal insufficiency and/or progressive leukodystrophy (cerebral ALD) at an early age. Pathogenic variants in ABCD1 result in elevated levels of very long-chain fatty acids (VLCFA), including C26:0-lysophosphatidylcholine (C26:0-LPC). Newborn screening for ALD enables prospective monitoring and timely therapeutic intervention, thereby preventing irreversible damage and saving lives. The Dutch Health Council recommended to screen only male newborns for ALD without identifying untreatable conditions associated with elevated C26:0-LPC, like Zellweger spectrum disorders and single peroxisomal enzyme defects. Here, we present the results of the SCAN (Screening for ALD in the Netherlands) study which is the first sex-specific newborn screening program worldwide. Males with ALD are identified based on elevated C26:0-LPC levels, the presence of one X-chromosome and a variant in ABCD1, in heel prick dried bloodspots. Screening of 71 208 newborns resulted in the identification of four boys with ALD who, following referral to the pediatric neurologist and confirmation of the diagnosis, enrolled in a long-term follow-up program. The results of this pilot show the feasibility of employing a boys-only screening algorithm that identifies males with ALD without identifying untreatable conditions. This approach will be of interest to countries that are considering ALD newborn screening but are reluctant to identify girls with ALD because for girls there is no direct health benefit. We also analyzed whether gestational age, sex, birth weight and age at heel prick blood sampling affect C26:0-LPC concentrations and demonstrate that these covariates have a minimal effect.

Adult-Onset Genetic Central Nervous System Disorders Masquerading as Acquired Neuroinflammatory Disorders: A Review

Importance

Adult-onset genetic disorders may present with clinical and magnetic resonance imaging (MRI) features suggestive of acquired inflammatory diseases. An ever-growing number of potentially treatable adult-onset genetic neuroinflammatory disorders have been described in the past few years that need to be rapidly identified.

Observations

Adult-onset acquired neuroinflammatory disorders encompass a large group of central nervous system (CNS) diseases with varying presentation, MRI characteristics, and course, among which the most common is multiple sclerosis. Despite recent progress, including the discovery of specific autoantibodies, a significant number of adult-onset neuroinflammatory disorders with progressive or relapsing course still remain without a definite diagnosis. In addition, some patients with genetic disorders such as leukodystrophies, hemophagocytic lymphohistiocytosis, or genetic vasculopathies can mimic acquired neuroinflammatory disorders. These genetic disorders, initially described in pediatric populations, are increasingly detected in adulthood thanks to recent progress in molecular genetics and the larger availability of high-throughput sequencing technologies.

Conclusions and Relevance

Genetic adult-onset neuroinflammatory diseases are at the border between primary CNS inflammatory diseases and systemic disorders with multiorgan involvement and predominantly neurologic manifestations. Neurologists must be aware of the main clues and red flags so they can confirm a diagnosis early, when some of these genetic disorders can be successfully treated.

Peroxisome Metabolism Contributes to PIEZO2-Mediated Mechanical Allodynia

Mutations in the peroxisomal half-transporter ABCD1 cause X-linked adrenoleukodystrophy, resulting in elevated very long-chain fatty acids (VLCFA), progressive neurodegeneration and an associated pain syndrome that is poorly understood. In the nervous system of mice, we found ABCD1 expression to be highest in dorsal root ganglia (DRG), with satellite glial cells (SGCs) displaying higher expression than neurons. We subsequently examined sensory behavior and DRG pathophysiology in mice deficient in ABCD1 compared to wild-type mice. Beginning at 8 months of age, Abcd1-/y mice developed persistent mechanical allodynia. DRG had a greater number of IB4-positive nociceptive neurons expressing PIEZO2, the mechanosensitive ion channel. Blocking PIEZO2 partially rescued the mechanical allodynia. Beyond affecting neurons, ABCD1 deficiency impacted SGCs, as demonstrated by high levels of VLCFA, increased glial fibrillary acidic protein (GFAP), as well as genes disrupting neuron-SGC connectivity. These findings suggest that lack of the peroxisomal half-transporter ABCD1 leads to PIEZO2-mediated mechanical allodynia as well as SGC dysfunction. Given the known supportive role of SGCs to neurons, this elucidates a novel mechanism underlying pain in X-linked adrenoleukodystrophy.

Sensorimotor outcomes in adrenomyeloneuropathy show significant disease progression

Current outcomes used to evaluate adrenomyeloneuropathy are limited by rater bias, not sensitive to preclinical changes, and require years to decades to detect disease progression. Quantitative outcomes are needed that detect meaningful change in a short time period over a broad range of disability. The study aim was to track sensorimotor outcomes in adults with adrenomyeloneuropathy and evaluate differences in progression between men and women. This prospective observational cohort study analyzes data collected annually in the Phase III study of adults with adrenomyeloneuropathy. Outcomes include postural sway in four static standing conditions, great-toe vibration, hip strength, walking velocity, timed up-and-go, and 6-minute walk distance. Linear mixed model analysis was used to detect change in the outcomes in 2 years, correcting for age, sex, disability, symptom duration, and treatment across the cohort. Modeling was repeated for each sex to evaluate differences. Power computations were carried out by sex and for the full dataset. Sixty-one men and 87 women participated. Average age, 46 ± 12 years; Expanded Disability Status Scale, 3 (1-6.5); symptom duration, 10.8 ± 9.4 years. The cohort showed significant worsening in all standing conditions (P < .001), sensation (P = .0223) and strength (P = .001); but more stability in walking with only velocity (P < .0337) significantly declining. For each sex, postural sway declines significantly in all conditions (P < .01) except for eyes closed feet together for women. Strength declines significantly by sex for hip flexion (P < .03). Sex-specific significant decline is seen in walking (velocity P = .0276; distance P = .0072) for men only. Quantitative measures of postural sway, sensation strength, and walking are effective measures of adrenomyeloneuropathy progression in 2 years.

The clinical spectrum of X-linked adrenoleukodystrophy: from Addison's-only in men to middle-age neurologic manifestations in women

X-linked adrenoleukodystrophy (X-ALD) is caused by a mutation in the ABCD1 gene which encodes for a peroxisomal very long-chain fatty acid (VLCFA) transporter. Clinically, X-ALD can present a wide range of phenotypes, from slowly progressive myelopathy to rapid demyelination of brain white matter (cerebral X-ALD-CALD). Adrenocortical insufficiency (AI) occurs mainly in the pediatric age group, and it can be the first manifestation of the disease. Female carriers may also develop manifestations of myelopathy, but later in life. We present two cases of patients who show the heterogeneous clinical manifestations of X-ALD. Case 1 was a man with AI diagnosed at 6 years old and with the first manifestations of myelopathy at 44 years old, which led to the diagnosis of X-ALD. At 47 years, he developed rapidly progressive CALD. Case 2 was a woman with progressive spastic gait disturbance that started at 49 years old. The diagnosis of X-ALD was confirmed at 54 years old after the discovery of a family history of the disease. Mild progression of the neurologic manifestations was noted, but with no signs of AI nor CALD. She is currently 60 years old and under surveillance. We review the current knowledge on X-ALD as concerns its genetic and pathophysiological mechanisms, clinical presentations, diagnosis, treatment, and follow-up. This condition is a real diagnostic challenge. The early detection of AI and CALD, potentially life-threatening complications in men, is very difficult. The surveillance of these complications in female patients still raises controversy.

Long-term disease prevention with a gene therapy targeting oligodendrocytes in a mouse model of adrenomyeloneuropathy

Adrenomyeloneuropathy (AMN) is a late-onset axonopathy of spinal cord tracts caused by mutations of the ABCD1 gene that encodes ALDP, a peroxisomal transporter of very long chain fatty acids (VLCFA). Disturbed metabolic interaction between oligodendrocytes (OL) and axons is suspected to play a major role in AMN axonopathy. To develop a vector targeting OL, the human ABCD1 gene driven by a short 0.3 kb part of the human myelin-associated glycoprotein (MAG) promoter was packaged into an adeno-associated viral serotype 9 (rAAV9). An intravenous injection of this vector at postnatal day 10 (P10) in Abcd1-/- mice, a model of AMN, allowed a near normal motor performance to persist for 24 months, while age-matched untreated mice developed major defects of balance and motricity. Three weeks post vector, 50-54% of spinal cord white matter OL were expressing ALDP at the cervical level, and only 6-7% after 24 months. In addition, 29-32% of cervical spinal cord astrocytes at 3 weeks and 16-19% at 24 months also expressed ALDP. C26:0-lysoPC, a sensitive VLCFA marker of AMN, was lower by 41% and 50%, respectively in the spinal cord and brain of vector-treated compared with untreated mice. In a non-human primate (NHP), the intrathecal injection of the rAAV9-MAG vector induced abundant ALDP expression at 3 weeks in spinal cord OL (43%, 29%, 26% at cervical, thoracic and lumbar levels) and cerebellum OL (35%). In addition, 33-41 % of spinal cord astrocytes expressed hALDP, and 27% of cerebellar astrocytes. To our knowledge, OL targeting had not been obtained before in primates with other vectors or promoters. The current results thus provide a robust proof-of-concept not only for the gene therapy of AMN but for other CNS diseases where the targeting of OL with the rAAV9-MAG vector may be of interest.

Structure and Function of the ABCD1 Variant Database: 20 Years, 940 Pathogenic Variants, and 3400 Cases of Adrenoleukodystrophy

The progressive neurometabolic disorder X-linked adrenoleukodystrophy (ALD) is caused by pathogenic variants in the ABCD1 gene, which encodes the peroxisomal ATP-binding transporter for very-long-chain fatty acids. The clinical spectrum of ALD includes adrenal insufficiency, myelopathy, and/or leukodystrophy. A complicating factor in disease management is the absence of a genotype–phenotype correlation in ALD. Since 1999, most ABCD1 (likely) pathogenic and benign variants have been reported in the ABCD1 Variant Database. In 2017, following the expansion of ALD newborn screening, the database was rebuilt. To add an additional level of confidence with respect to pathogenicity, for each variant, it now also reports the number of cases identified and, where available, experimental data supporting the pathogenicity of the variant. The website also provides information on a number of ALD-related topics in several languages. Here, we provide an updated analysis of the known variants in ABCD1. The order of pathogenic variant frequency, overall clustering of disease-causing variants in exons 1–2 (transmembrane domain spanning region) and 6–9 (ATP-binding domain), and the most commonly reported pathogenic variant p.Gln472Argfs*83 in exon 5 are consistent with the initial reports of the mutation database. Novel insights include nonrandom clustering of high-density missense variant hotspots within exons 1, 2, 6, 8, and 9. Perhaps more importantly, we illustrate the importance of collaboration and utility of the database as a scientific, clinical, and ALD-community-wide resource.

Functional electrical stimulation to aid walking in patients with adrenomyeloneuropathy: A case study and observational series

Adrenomyeloneuropathy (AMN) is a rare inherited condition where affected individuals develop slowly progressive spastic paraparesis with a gradual decline in walking ability. There is no cure for AMN and treatment focuses on supportive measures and aids. One treatment option is functional electrical stimulation (FES), a treatment, approved by The National Institute for Health and Care Excellence (NICE), for managing foot drop in upper motor neuron disorders. Limited evidence exists for its use in AMN patients. We describe the effects of FES in an individual case and more broadly within a cohort of 21 patients successfully treated with FES. Patients with AMN referred for FES typically report frequent falls (71%) and foot drop (57%) as the most common barriers to walking. When using FES, walking speed at baseline (0.70 m/s [SD = 0.2]) was maintained at the 2-year review (0.68 m/s [SD = 0.2]) with a persistent orthotic effect (improvement in walking speed when device on vs. off) seen from wearing FES over the same 2-year period (11%-19%). Patient walking satisfaction (visual analogue scale: 0 - very dissatisfied; 10 - very satisfied) was also greater when comparing no-FES versus FES over the same period (Year 1: 2.5 vs. 7.7; Year 2: 2.1 vs. 6.1). FES is not effective in all patients. Twelve patients referred found no benefit from the device; although there was no clear evidence, this was related to the degree of AMN associated peripheral neuropathy. However, FES is a safe, cost-effective treatment option and should be considered, along with assessment in a multidisciplinary clinic, for all AMN patients with walking difficulties.

Discovery of Novel, Orally Bioavailable Pyrimidine Ether-Based Inhibitors of ELOVL1

In our efforts to identify novel small molecule inhibitors for the treatment of adrenoleukodystrophy (ALD), we conducted a high-throughput radiometric screen for inhibitors of elongation of very long chain fatty acid 1 (ELOVL1) enzyme. We developed a series of highly potent, central nervous system (CNS)-penetrant pyrimidine ether-based compounds with favorable pharmacokinetics culminating in compound 22. Compound 22 is a selective inhibitor of ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts and lymphocytes in vitro. Compound 22 reduced C26:0 lysophosphatidyl choline (LPC), a subtype of VLCFA, in the blood of ATP binding cassette transporter D1 (ABCD1) KO mice, a murine model of ALD to near wild-type levels. Compound 22 is a low-molecular-weight, potent ELOVL1 inhibitor that may serve as a useful tool for exploring therapeutic approaches to the treatment of ALD.

Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27─a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Molecular Biomarkers for Adrenoleukodystrophy: An Unmet Need

X-linked adrenoleukodystrophy (ALD) is an inherited progressive neurometabolic disease caused by mutations in the ABCD1 gene and the accumulation of very long-chain fatty acids in plasma and tissues. Patients present with heterogeneous clinical manifestations which can include adrenal insufficiency, myelopathy, and/or cerebral demyelination. In the absence of a genotype-phenotype correlation, the clinical outcome of an individual cannot be predicted and currently there are no molecular markers available to quantify disease severity. Therefore, there is an unmet clinical need for sensitive biomarkers to monitor and/or predict disease progression and evaluate therapy efficacy. The increasing amount of biological sample repositories ('biobanking') as well as the introduction of newborn screening creates a unique opportunity for identification and evaluation of new or existing biomarkers. Here we summarize and review the many studies that have been performed to identify and improve knowledge surrounding candidate molecular biomarkers for ALD. We also highlight several shortcomings of ALD biomarker studies, which often include a limited sample size, no collection of longitudinal data, and no validation of findings in an external cohort. Nonetheless, these studies have generated a list of interesting biomarker candidates and this review aspires to direct future biomarker research.

Biochemical Studies in Fibroblasts to Interpret Variants of Unknown Significance in the ABCD1 Gene

Due to newborn screening for X-linked adrenoleukodystrophy (ALD), and the use of exome sequencing in clinical practice, the detection of variants of unknown significance (VUS) in the ABCD1 gene is increasing. In these cases, functional tests in fibroblasts may help to classify a variant as (likely) benign or pathogenic. We sought to establish reference ranges for these tests in ALD patients and control subjects with the aim of helping to determine the pathogenicity of VUS in ABCD1. Fibroblasts from 36 male patients with confirmed ALD, 26 healthy control subjects and 17 individuals without a family history of ALD, all with an uncertain clinical diagnosis and a VUS identified in ABCD1, were included. We performed a combination of tests: (i) a test for very-long-chain fatty acids (VLCFA) levels, (ii) a D₃-C22:0 loading test to study the VLCFA metabolism and (iii) immunoblotting for ALD protein. All ALD patient fibroblasts had elevated VLCFA levels and a reduced peroxisomal ß-oxidation capacity (as measured by the D₃-C16:0/D₃-C22:0 ratio in the D₃-C22:0 loading test) compared to the control subjects. Of the VUS cases, the VLCFA metabolism was not significantly impaired (most test results were within the reference range) in 6/17, the VLCFA metabolism was significantly impaired (most test results were within/near the ALD range) in 9/17 and a definite conclusion could not be drawn in 2/17 of the cases. Biochemical studies in fibroblasts provided clearly defined reference and disease ranges for the VLCFA metabolism. In 15/17 (88%) VUS we were able to classify the variant as being likely benign or pathogenic. This is of great clinical importance as new variants will be detected.

Management of adrenoleukodystrophy: From pre-clinical studies to the development of new therapies

X-linked adrenoleukodystrophy (X-ALD) is an inherited neurodegenerative disorder associated with mutations of the ABCD1 gene that encodes a peroxisomal transmembrane protein. It results in accumulation of very long chain fatty acids in tissues and body fluid. Along with other factors such as epigenetic and environmental involvement, ABCD1 mutation-provoked disorders can present different phenotypes including cerebral adrenoleukodystrophy (cALD), adrenomyeloneuropathy (AMN), and peripheral neuropathy. cALD is the most severe form that causes death in young childhood. Bone marrow transplantation and hematopoietic stem cell gene therapy are only effective when performed at an early stage of onsets in cALD. Nonetheless, current research and development of novel therapies are hampered by a lack of in-depth understanding disease pathophysiology and a lack of reliable cALD models. The Abcd1 and Abcd1/Abcd2 knock-out mouse models as well as the deficiency of Abcd1 rabbit models created in our lab, do not develop cALD phenotypes observed in human beings. In this review, we summarize the clinical and biochemical features of X-ALD, the progress of pre-clinical and clinical studies. Challenges and perspectives for future X-ALD studies are also discussed.

Diverse clinical manifestations of X-linked adrenoleukodystrophy in a Chinese family with identical multisite variants of ABCD1 gene

OBJECTIVE

This study summarized the clinical characteristics of X-linked adrenoleukodystrophy (X-ALD) patients in this family, and two different manifestations of the same variants in a Chinese family were reported in this article. That conducted a follow-up study to further clarify the characteristics of this disease.

BASIC METHODS

Clinical data and test results were analyzed, and the exon region of ALD-related gene ABCD1 was sequenced by Sanger sequencing.

MAIN RESULTS

Gene analysis showed that there were three ABCD1 variants in the proband, c.1047C>A, c.1415-1416delAG and c.1548G>A. The elder brother of the proband had the same three variants as the proband, but showed different clinical symptoms. The mother was the carrier of three variants. Multisite variants were uncovered in this family, which caused two different manifestations of adult-onset childhood cerebral ALD and adrenomyeloneuropathy.

PRINCIPAL CONCLUSION

These findings further increase our knowledge about ABCD1 mutations and the associated phenotypes, which is beneficial for the genetic counseling of patients with X-ALD.

Magnetic resonance spectroscopy as marker for neurodegeneration in X-linked adrenoleukodystrophy

X-linked adrenoleukodsytrophy (ALD) is a genetic neuro-metabolic disorder, causing a slowly progressive myelopathy in adult male and female patients. New disease modifying therapies for myelopathy are under development. This calls for new (imaging) markers able to measure disease severity and progression in clinical trials. In this prospective cohort study, we measured cerebral metabolite levels with Magnetic Resonance Spectroscopy (MRS), and evaluated their potential as biomarkers for disease severity and neurodegeneration in ALD. We used a comprehensive protocol of 3T Magnetic Resonance Spectroscopic Imaging (MRSI) and 7T Single Voxel Spectroscopy (SVS) in a large cohort of adult ALD males without cerebral demyelination. One hundred seven baseline scans - 59 obtained in ALD patients (42 3T MRSI and 17 7T SVS) and 48 obtained in healthy male controls (32 3T MRSI and 16 7T SVS) - and 82 one and two-year follow-up scans (66 3T MRSI and 16 7T SVS) of ALD patients were included. Both protocols showed significantly lower concentration ratios of N-acetylaspartate/creatine (tNAA/tCr) and Glx (glutamine + glutamate)/tCr in the grey and white matter of patients, compared to controls. A novel finding is the higher level of inositol (Ins)/tCr and choline containing compounds (tCho)/tCr in ALD patients without cerebral demyelination. Furthermore, tNAA/tCr correlated strongly with clinical measures of severity of myelopathy. There was no detectable change in metabolite ratios after one-year or two-year follow-up. Our results imply that cerebral metabolite levels - and more specifically the tNAA/tCr ratio - measured with MRS, have potential value as (imaging) biomarkers in ALD.

Imaging in X-Linked Adrenoleukodystrophy

Magnetic resonance imaging (MRI) is the gold standard for the detection of cerebral lesions in X-linked adrenoleukodystrophy (ALD). ALD is one of the most common peroxisomal disorders and is characterized by a defect in degradation of very long chain fatty acids (VLCFA), resulting in accumulation of VLCFA in plasma and tissues. The clinical spectrum of ALD is wide and includes adrenocortical insufficiency, a slowly progressive myelopathy in adulthood, and cerebral demyelination in a subset of male patients. Cerebral demyelination (cerebral ALD) can be treated with hematopoietic cell transplantation (HCT) but only in an early (pre- or early symptomatic) stage and therefore active MRI surveillance is recommended for male patients, both pediatric and adult. Although structural MRI of the brain can detect the presence and extent of cerebral lesions, it does not predict if and when cerebral demyelination will occur. There is a great need for imaging techniques that predict onset of cerebral ALD before lesions appear. Also, imaging markers for severity of myelopathy as surrogate outcome measure in clinical trials would facilitate drug development. New quantitative MRI techniques are promising in that respect. This review focuses on structural and quantitative imaging techniques-including magnetic resonance spectroscopy, diffusion tensor imaging, MR perfusion imaging, magnetization transfer (MT) imaging, neurite orientation dispersion and density imaging (NODDI), and myelin water fraction imaging-used in ALD and their role in clinical practice and research opportunities for the future.

Gait Difficulties and Postural Instability in Adrenoleukodystrophy

Background: Gait and balance difficulties are among the most common clinical manifestations in adults with X-linked adrenoleukodystrophy, but little is known about the contributions of sensory loss, motor dysfunction, and postural control to gait dysfunction and fall risk.

Objective: To quantify gait and balance deficits in both males and females with adrenoleukodystrophy and evaluate how environmental perturbations (moving surfaces and visual surrounds) affect balance and fall risk.

Methods: We assessed sensory and motor contributions to gait and postural instability in 44 adult patients with adrenoleukodystrophy and 17 healthy controls using three different functional gait assessments (25 Foot Walk test, Timed Up and Go, and 6 Minute Walk test) and computerized dynamic posturography.

Results: The median Expanded Disability Status Scale score for the patient cohort was 3.0 (range 0.0–6.5). Both males and females with adrenoleukodystrophy showed impairments on all three functional gait assessments relative to controls (P < 0.001). Performance on walking tests and Expanded Disability Status Scale scores correlated with incidence of falls on computerized dynamic posturography, with the 25 Foot Walk being a moderately reliable predictor of fall risk (area under the ROC curve = 0.7675, P = 0.0038).

Conclusion: We demonstrate that gait difficulties and postural control deficits occur in patients with adrenoleukodystrophy, albeit at an older age in females. Postural deficits were aggravated by eyes closed and dynamic conditions that rely on vestibular input, revealing challenges to the interplay of motor, sensory and vestibular circuitry in adrenoleukodystrophy.

Bone marrow transplantation into Abcd1-deficient mice: Distribution of donor derived-cells and biological characterization of the brain of the recipient mice

X-linked adrenoleukodystrophy (X-ALD) is a severe inherited metabolic disease with cerebral inflammatory demyelination and abnormal accumulation of very long chain fatty acid (VLCFA) in tissues, especially the brain. At present, bone marrow transplantation (BMT) at an early stage of the disease is the only effective treatment for halting disease progression, but the underlying mechanism of the treatment has remained unclear. Here, we transplanted GFP-expressing wild-type (WT) or Abcd1-deficient (KO) bone marrow cells into recipient KO mice, which enabled tracking of the donor GFP⁺ cells in the recipient mice. Both the WT and KO donor cells were equally distributed throughout the brain parenchyma, and displayed an Iba1-positive, GFAP- and Olig2-negative phenotype, indicating that most of the donor cells were engrafted as microglia-like cells. They constituted approximately 40% of the Iba1-positive cells. Unexpectedly, no decrease of VLCFA in the cerebrum was observed when WT bone marrow cells were transplanted into KO mice. Taken together, murine study suggests that bone marrow-derived microglia-like cells engrafted in the cerebrum of X-ALD patients suppress disease progression without evidently reducing the amount of VLCFA in the cerebrum.

Optical coherence tomography to measure the progression of myelopathy in adrenoleukodystrophy

OBJECTIVE

To prospectively determine the value of optical coherence tomography (OCT) as a surrogate outcome measure for the progression of myelopathy in males with adrenoleukodystrophy.

METHODS

Retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness were measured at baseline, 1- and 2-year follow-up in patients and age-matched controls. We assessed the severity of myelopathy with clinical parameters: Expanded Disability Status Scale (EDSS), Severity Scoring system for Progressive Myelopathy (SSPROM), and timed up-and-go. Linear mixed model analysis was used to compare changes in retinal layer thickness of patients to controls. In addition, we correlated changes in retinal layer thickness with changes in clinical parameters.

RESULTS

Longitudinal data were available for 28 patients and 29 controls. Peripapillary RNFL (pRNFL) thickness decreased significantly in patients compared to controls (-1.75µm, p = 0.001), whereas change in macular GCL and RNFL was not different between groups. Analysis of the symptomatic subgroup showed that, apart from a similar decrease in pRNFL thickness, GCL thickness decreased significantly (-0.55 µm, p = 0.014). There were moderately strong correlations between changes in retinal layer thickness and changes in clinical parameters of severity of myelopathy.

INTERPRETATION

This prospective study demonstrates the potential of OCT-measured retinal neurodegeneration as a surrogate outcome measure for the progression of myelopathy in adrenoleukodystrophy. As differences were small, our findings need to be confirmed with longer follow-up and/or in a larger patient sample.

Neurofilament light chain as a potential biomarker for monitoring neurodegeneration in X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD), the most frequent monogenetic disorder of brain white matter, is highly variable, ranging from slowly progressive adrenomyeloneuropathy (AMN) to life-threatening inflammatory brain demyelination (CALD). In this study involving 94 X-ALD patients and 55 controls, we tested whether plasma/serum neurofilament light chain protein (NfL) constitutes an early distinguishing biomarker. In AMN, we found moderately elevated NfL with increased levels reflecting higher grading of myelopathy-related disability. Intriguingly, NfL was a significant predictor to discriminate non-converting AMN from cohorts later developing CALD. In CALD, markedly amplified NfL levels reflected brain lesion severity. In rare cases, atypically low NfL revealed a previously unrecognized smoldering CALD disease course with slowly progressive myelin destruction. Upon halt of brain demyelination by hematopoietic stem cell transplantation, NfL gradually normalized. Together, our study reveals that blood NfL reflects inflammatory activity and progression in CALD patients, thus constituting a potential surrogate biomarker that may facilitate clinical decisions and therapeutic development.

Multiparametric in vivo analyses of the brain and spine identify structural and metabolic biomarkers in men with adrenomyeloneuropathy

OBJECTIVE

Progressive myelopathy causes severe handicap in men with adrenomyeloneuropathy (AMN), an X-linked disorder due to ABCD1 pathogenic variants. At present, treatments are symptomatic but disease-modifying therapies are under evaluation. Given the small effect size of clinical scales in AMN, biomarkers with higher effect size are needed. Here we used high-resolution magnetic resonance techniques to identify non-invasive in vivo biomarkers of the brain and spine with high effect sizes.

METHODS

We performed a multiparametric imaging and spectroscopy study in 23 male patients with AMN (age: 44 ± 11) and 23 male controls (age: 43 ± 11) of similar age and body-mass index. We combined (i) macrostructural analyses of the spine, using cross-sectional area (CSA) and magnetization transfer ratio (MTR), (ii) microstructural analyses of the spine and the brain, using diffusion tensor and the newly developed fixel-based analysis, and (iii) advanced metabolic analyses of the spine using metabolite cycling coupled to a semi-LASER sequences.

RESULTS

Macrostructural alterations (decrease in CSA and MTR) were observed in patients at all spinal cord levels studied (C1-T2 for CSA and C1-C5 for MTR) (p < 0.001). Microstructural alterations were observed in the spine and brain on diffusion tensor and fixel-based metrics though the latter showed higher effect sizes. Metabolic alterations were observed in patients as a decreased total N-acetylaspartate/myo-inositol ratio (p < 0.001). Overall, MTR showed the highest effect size.

CONCLUSION

This cross-sectional study supports the use of multiparametric techniques that elucidate the structural, microstructural and metabolic alterations in AMN. These outcome measures should be tested longitudinally and in clinical trials.

Beyond gait and balance: urinary and bowel dysfunction in X-linked adrenoleukodystrophy

Objective

To characterize the prevalence, onset, and burden of urinary and bowel dysfunction in adult patients with adrenoleukodystrophy (ALD) and to evaluate any sex differences in symptom presentation.

Methods

In this retrospective and prospective study, we performed medical record review (n = 103), analyzed the results of clinically indicated urodynamic testing (n = 11), and developed and distributed a symptom and quality of life (QOL) survey (n = 59).

Results

Urinary and bowel symptoms are highly prevalent in both males (75.0%) and females (78.8%) in this population, most commonly urinary urgency, often leading to incontinence. Time to onset of first urinary or bowel symptom occurs approximately a decade earlier in males. Seventy-two percent of symptomatic patients report a limitation to QOL. Urodynamic evaluation provides evidence of three distinct mechanisms underlying lower urinary tract dysfunction: involuntary detrusor contractions (indicating uncontrolled neuronal stimulation with or without leakage), motor underactivity of the bladder, and asynergy between detrusor contraction and sphincter relaxation.

Conclusions

Beyond gait and balance difficulties, urinary and bowel symptoms are common in adults with ALD and impair QOL. Males are affected at a younger age but both sexes experience a higher symptom burden with age. As this population also experiences gait and balance impairment, patients with ALD are more vulnerable to urinary urgency leading to incontinence. Urodynamic evaluation may help better elucidate the pathophysiologic mechanisms underlying neurogenic lower urinary tract dysfunction, which can allow more targeted treatment.

Endocrine dysfunction in adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a peroxisomal disorder caused by mutations in the ABCD1 gene and characterized by impaired very long-chain fatty acid beta-oxidation. Clinically, male patients develop adrenal failure and a progressive myelopathy in adulthood, although age of onset and rate of progression are highly variable. Additionally, 40% of male patients develop a leukodystrophy (cerebral ALD) before the age of 18 years. Women with ALD also develop a myelopathy but generally at a later age than men and with slower progression. Adrenal failure and leukodystrophy are exceedingly rare in women. Allogeneic hematopoietic cell transplantation (HCT), or more recently autologous HCT with ex vivo lentivirally transfected bone marrow, halts the leukodystrophy. Unfortunately, there is no curative treatment for the myelopathy. In the following chapter, the biochemistry, pathology, and clinical spectrum of ALD are discussed in detail.

Plasma NfL and GFAP as biomarkers of spinal cord degeneration in adrenoleukodystrophy

OBJECTIVE

To explore the potential of neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) as biomarkers of spinal cord degeneration in adrenoleukodystrophy, as objective treatment-outcome parameters are needed.

METHODS

Plasma NfL and GFAP levels were measured in 45 male and 47 female ALD patients and compared to a reference cohort of 73 healthy controls. For male patients, cerebrospinal fluid (CSF) samples (n = 33) and 1-year (n = 39) and 2-year (n = 18) follow-up data were also collected. Severity of myelopathy was assessed with clinical parameters: Expanded Disability Status Scale (EDSS), Severity Scoring system for Progressive Myelopathy (SSPROM), and timed up-and-go.

RESULTS

NfL and GFAP levels were higher in male (P < 0.001, effect size (partial ƞ² ) NfL = 0.49, GFAP = 0.13) and female (P < 0.001, effect size NfL = 0.19, GFAP = 0.23) patients compared to controls; levels were higher in both symptomatic and asymptomatic patients. In male patients, NfL levels were associated with all three clinical parameters of severity of myelopathy (EDSS, SSPROM, and timed up-and go), while GFAP in male and NfL and GFAP in female patients were not. Changes in clinical parameters during follow-up did not correlate with (changes in) NfL or GFAP levels. Plasma and CSF NfL were strongly correlated (r = 0.60, P < 0.001), but plasma and CSF GFAP were not (r = 0.005, P = 0.98).

INTERPRETATION

Our study illustrates the potential of plasma NfL as biomarker of spinal cord degeneration in adrenoleukodystrophy, which was superior to plasma GFAP in our cohort.

Postural Body Sway as Surrogate Outcome for Myelopathy in Adrenoleukodystrophy

Background

Myelopathy is the core clinical manifestation of adrenoleukodystrophy (ALD), which is the most common peroxisomal disorder. Development of therapies requires sensitive and clinically relevant outcome measures. Together with spastic paraparesis, balance disturbance is the main cause of disability from myelopathy in ALD. In this cross-sectional study, we evaluated whether postural body sway - a measure of balance - could serve as a surrogate outcome in clinical trials.

Methods

Forty-eight male ALD patients and 49 age-matched healthy male controls were included in this study. We compared sway amplitude and sway path of ALD patients to controls. We then correlated the body sway parameters showing the largest between-group differences with clinical measures of severity of myelopathy. To correct for age, we performed multiple linear regression analysis with age and severity of myelopathy as independent variables.

Results

All body sway parameters were significantly higher in patients than in controls, with medium to large effect sizes (r = 0.43-0.66, p < 0.001). In the subgroup of asymptomatic patients, body sway amplitude was also higher, but the difference with controls was smaller than for symptomatic patients (effect size r = 0.38-0.46). We found moderate to strong correlations between body sway amplitude and clinical severity of myelopathy (r = 0.40-0.79, p < 0.005). After correction for age, severity of myelopathy was a significant predictor of body sway amplitude in all regression models.

Conclusions

These results indicate that postural body sway may serve as a surrogate outcome for myelopathy in ALD. Such outcomes are important to evaluate new therapies in clinical trials. Further longitudinal studies are needed and ongoing in this cohort.

Spinal cord atrophy as a measure of severity of myelopathy in adrenoleukodystrophy

All men and most women with X-linked adrenoleukodystrophy (ALD) develop myelopathy in adulthood. As clinical trials with new potential disease-modifying therapies are emerging, sensitive outcome measures for quantifying myelopathy are needed. This prospective cohort study evaluated spinal cord size (cross-sectional area - CSA) and shape (eccentricity) as potential new quantitative outcome measures for myelopathy in ALD. Seventy-four baseline magnetic resonance imaging (MRI) scans, acquired in 42 male ALD patients and 32 age-matched healthy controls, and 26 follow-up scans of ALD patients were included in the study. We used routine T1 -weighted MRI sequences to measure mean CSA, eccentricity, right-left and anteroposterior diameters in the cervical spinal cord. We compared MRI measurements between groups and correlated CSA with clinical outcome measures of disease severity. Longitudinally, we compared MRI measurements between baseline and 1-year follow-up. CSA was significantly smaller in patients compared to controls on all measured spinal cord levels (P < .001). The difference was completely explained by the effect of the symptomatic subgroup. Furthermore, the spinal cord showed flattening (higher eccentricity and smaller anteroposterior diameters) in patients. CSA correlated strongly with all clinical measures of severity of myelopathy. There was no detectable change in CSA after 1-year follow-up. The cervical spinal cord in symptomatic ALD patients is smaller and flattened compared to controls, possibly due to atrophy of the dorsal columns. CSA is a reliable marker of disease severity and can be a valuable outcome measure in long-term follow-up studies in ALD. SYNOPSIS: A prospective cohort study in 42 adrenoleukodystrophy (ALD) patients and 32 controls demonstrated that the spinal cord cross-sectional area of patients is smaller compared to healthy controls and correlates with severity of myelopathy in patients, hence it could be valuable as a much needed surrogate outcome measure.

Multi-Omic Approach to Identify Phenotypic Modifiers Underlying Cerebral Demyelination in X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a peroxisomal metabolic disorder with a highly complex clinical presentation. ALD is caused by mutations in the ABCD1 gene, and is characterized by the accumulation of very long-chain fatty acids in plasma and tissues. Disease-causing mutations are 'loss of function' mutations, with no prognostic value with respect to the clinical outcome of an individual. All male patients with ALD develop spinal cord disease and a peripheral neuropathy in adulthood, although age of onset is highly variable. However, the lifetime prevalence to develop progressive white matter lesions, termed cerebral ALD (CALD), is only about 60%. Early identification of transition to CALD is critical since it can be halted by allogeneic hematopoietic stem cell therapy only in an early stage. The primary goal of this study is to identify molecular markers which may be prognostic of cerebral demyelination from a simple blood sample, with the hope that blood-based assays can replace the current protocols for diagnosis. We collected six well-characterized brother pairs affected by ALD and discordant for the presence of CALD and performed multi-omic profiling of blood samples including genome, epigenome, transcriptome, metabolome/lipidome, and proteome profiling. In our analysis we identify discordant genomic alleles present across all families as well as differentially abundant molecular features across the omics technologies. The analysis was focused on univariate modeling to discriminate the two phenotypic groups, but was unable to identify statistically significant candidate molecular markers. Our study highlights the issues caused by a large amount of inter-individual variation, and supports the emerging hypothesis that cerebral demyelination is a complex mix of environmental factors and/or heterogeneous genomic alleles. We confirm previous observations about the role of immune response, specifically auto-immunity and the potential role of PFN1 protein overabundance in CALD in a subset of the families. We envision our methodology as well as dataset has utility to the field for reproducing previous or enabling future modifier investigations.

X-linked adrenoleukodystrophy: Pathology, pathophysiology, diagnostic testing, newborn screening and therapies

Adrenoleukodystrophy (ALD) is a rare X-linked disease caused by a mutation of the peroxisomal ABCD1 gene. This review summarizes our current understanding of the pathogenic cell- and tissue-specific roles of lipid species in the context of experimental therapeutic strategies and provides an overview of critical historical developments, therapeutic trials and the advent of newborn screening in the USA. In ALD, very long-chain fatty acid (VLCFA) chain length-dependent dysregulation of endoplasmic reticulum stress and mitochondrial radical generating systems inducing cell death pathways has been shown, providing the rationale for therapeutic moiety-specific VLCFA reduction and antioxidant strategies. The continuing increase in newborn screening programs and promising results from ongoing and recent therapeutic investigations provide hope for ALD.

Fatty Acid Oxidation in Peroxisomes: Enzymology, Metabolic Crosstalk with Other Organelles and Peroxisomal Disorders

Peroxisomes play a central role in metabolism as exemplified by the fact that many genetic disorders in humans have been identified through the years in which there is an impairment in one or more of these peroxisomal functions, in most cases associated with severe clinical signs and symptoms. One of the key functions of peroxisomes is the β-oxidation of fatty acids which differs from the oxidation of fatty acids in mitochondria in many respects which includes the different substrate specificities of the two organelles. Whereas mitochondria are the main site of oxidation of medium-and long-chain fatty acids, peroxisomes catalyse the β-oxidation of a distinct set of fatty acids, including very-long-chain fatty acids, pristanic acid and the bile acid intermediates di- and trihydroxycholestanoic acid. Peroxisomes require the functional alliance with multiple subcellular organelles to fulfil their role in metabolism. Indeed, peroxisomes require the functional interaction with lysosomes, lipid droplets and the endoplasmic reticulum, since these organelles provide the substrates oxidized in peroxisomes. On the other hand, since peroxisomes lack a citric acid cycle as well as respiratory chain, oxidation of the end-products of peroxisomal fatty acid oxidation notably acetyl-CoA, and different medium-chain acyl-CoAs, to CO₂ and H₂O can only occur in mitochondria. The same is true for the reoxidation of NADH back to NAD⁺. There is increasing evidence that these interactions between organelles are mediated by tethering proteins which bring organelles together in order to allow effective exchange of metabolites. It is the purpose of this review to describe the current state of knowledge about the role of peroxisomes in fatty acid oxidation, the transport of metabolites across the peroxisomal membrane, its functional interaction with other subcellular organelles and the disorders of peroxisomal fatty acid β-oxidation identified so far in humans.

Family Perspectives on Newborn Screening for X-Linked Adrenoleukodystrophy in California

X-linked adrenoleukodystrophy (ALD) is caused by gene variants in the ABCD1 gene, resulting in a varied clinical spectrum. Males with ALD present with symptoms ranging from isolated adrenal insufficiency and slowly progressive myelopathy to severe cerebral demyelination. Females who are heterozygous for ALD typically develop milder symptoms by late adulthood. Treatment for adrenal insufficiency associated with ALD exists in the form of cortisol, and cerebral ALD may be treated with stem cell transplantation. Currently, there is no treatment for myelopathy. Since 2013, at least 14 states have added ALD to their newborn screening (NBS) panel, including California in 2016. We examined the impact of a positive NBS result for ALD on families in California. Qualitative interviews were conducted with mothers of 10 children who were identified via NBS for ALD. Interviews were transcribed verbatim and analyzed using thematic analysis by two coders. Mothers felt strongly that ALD should be included on California's NBS panel; however, many expressed concerns over their experience. Themes included stress at initial phone call, difficulty living with uncertainty, concerns regarding mental health support, and desire for more information on disease progression, treatments and clinical trials. Mothers exhibited diverse coping strategies, including relying on faith, information seeking, and maintaining hope. Mothers' recommendations for healthcare providers included: educating providers making the initial phone call, providing patient-friendly resources, offering information about ongoing research, and streamlining care coordination. Advice for parents of children with ALD focused on staying hopeful and appreciating the time they have with their children. As more states add ALD to their NBS panel, it is important to improve the current model to promote family resiliency and autonomy.

X-linked Adrenoleukodystrophy: Pathology, Pathophysiology, Diagnostic Testing, Newborn Screening, and Therapies

Adrenoleukodystrophy (ALD) is a rare X-linked disease caused by a mutation of the peroxisomal ABCD1 gene. This review summarizes our current understanding of the pathogenic cell- and tissue-specific role of lipid species in the context of experimental therapeutic strategies and provides an overview of critical historical developments, therapeutic trials, and the advent of newborn screening in the United States. In ALD, very long chain fatty acid (VLCFA) chain-length-dependent dysregulation of endoplasmic reticulum stress and mitochondrial radical generating systems inducing cell death pathways has been shown, providing the rationale for therapeutic moiety-specific VLCFA reduction and antioxidant strategies. The continuing increase in newborn screening programs and promising results from ongoing and recent therapeutic investigations provide hope for ALD.

Longitudinal diffusion MRI as surrogate outcome measure for myelopathy in adrenoleukodystrophy

Objective

To prospectively determine the potential of diffusion MRI (dMRI) of the cervical spinal cord and the corticospinal tracts in brain as surrogate outcome measure for progression of myelopathy in men with adrenoleukodystrophy, as better outcome measures to quantify progression of myelopathy would enable clinical trials with fewer patients and shorter follow-up.

Methods

Clinical assessment of myelopathy included Expanded Disability Status Scale (EDSS), Severity Scoring System for Progressive Myelopathy (SSPROM), Timed Up-and-Go, and 6-Minute Walk Test. Applied dMRI metrics included fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity.

Results

Data were available for 33 controls and 52 patients. First, cross-sectionally, differences between groups (controls vs patients; controls vs asymptomatic patients vs symptomatic patients) were statistically significant for fractional anisotropy, mean diffusivity, and radial diffusivity in spinal cord and brain corticospinal tracts (effect size 0.31–0.68). Correlations between dMRI metrics and clinical measures were moderate to strong (correlation coefficient 0.35–0.60). Second, longitudinally (n = 36), change on clinical measures was significant after 2-year follow-up for EDSS, SSPROM, and Timed Up-and-Go (p ≤ 0.021, effect size ≤0.14). Change on brain fractional anisotropy and radial diffusivity was slightly larger (p ≤ 0.002, effect sizes 0.16–0.28). In addition, a statistically significant change was detectable in asymptomatic patients using brain dMRI and not using the clinical measures. Change on clinical measures did not correlate to change on dMRI metrics.

Conclusion

Although effect sizes were small, our prospective data illustrate the potential of dMRI as surrogate outcome measure for progression of myelopathy in men with adrenoleukodystrophy.

Optical coherence tomography shows neuroretinal thinning in myelopathy of adrenoleukodystrophy

Background

Progressive myelopathy is the main cause of disability in adrenoleukodystrophy (ALD). Development of therapies is hampered by a lack of quantitative outcome measures. In this study, we investigated whether myelopathy in ALD is associated with retinal neurodegeneration on optical coherence tomography (OCT), which could serve as a surrogate outcome measure.

Methods

Sixty-two patients (29 men and 33 women) and 70 age-matched and sex-matched controls (33 men and 37 women) were included in this cross-sectional study. We compared retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) and peripapillary retinal nerve fiber layer (pRNFL) thickness between ALD patients and controls. In addition, we correlated these OCT measurements with clinical parameters of severity of myelopathy.

Results

Patients had significantly thinner RNFL (male group, p < 0.05) and pRNFL superior and temporal quadrant [both male (p < 0.005) and female (p < 0.05) groups] compared to controls. Comparing three groups (symptomatic patients, asymptomatic patients and controls), there were significant differences in RNFL thickness (total grid and peripheral ring) in the male group (p ≤ 0.002) and in pRNFL thickness (superior and temporal quadrant) in both male (p ≤ 0.02) and the female (p ≤ 0.02) groups. Neuroretinal layer thickness correlated moderately with severity of myelopathy in men (correlation coefficients between 0.29–0.55, p < 0.02), but not in women.

Conclusions

These results suggest that neurodegeneration of the spinal cord in ALD is reflected in the retina of patients with ALD. Therefore, OCT could be valuable as an outcome measure for the myelopathy of ALD. Additional longitudinal studies are ongoing.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09627-z) contains supplementary material, which is available to authorized users.