Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision

In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.

Mutations in SLC39A14 disrupt manganese homeostasis and cause childhood-onset parkinsonism-dystonia

Although manganese is an essential trace metal, little is known about its transport and homeostatic regulation. Here we have identified a cohort of patients with a novel autosomal recessive manganese transporter defect caused by mutations in SLC39A14. Excessive accumulation of manganese in these patients results in rapidly progressive childhood-onset parkinsonism-dystonia with distinctive brain magnetic resonance imaging appearances and neurodegenerative features on post-mortem examination. We show that mutations in SLC39A14 impair manganese transport in vitro and lead to manganese dyshomeostasis and altered locomotor activity in zebrafish with CRISPR-induced slc39a14 null mutations. Chelation with disodium calcium edetate lowers blood manganese levels in patients and can lead to striking clinical improvement. Our results demonstrate that SLC39A14 functions as a pivotal manganese transporter in vertebrates.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 2: the evolving clinical phenotype

BACKGROUND

The disease course and long-term outcome of patients with organic acidurias (OAD) and urea cycle disorders (UCD) are incompletely understood.

AIMS

To evaluate the complex clinical phenotype of OAD and UCD patients at different ages.

RESULTS

Acquired microcephaly and movement disorders were common in OAD and UCD highlighting that the brain is the major organ involved in these diseases. Cardiomyopathy [methylmalonic (MMA) and propionic aciduria (PA)], prolonged QTc interval (PA), optic nerve atrophy [MMA, isovaleric aciduria (IVA)], pancytopenia (PA), and macrocephaly [glutaric aciduria type 1 (GA1)] were exclusively found in OAD patients, whereas hepatic involvement was more frequent in UCD patients, in particular in argininosuccinate lyase (ASL) deficiency. Chronic renal failure was often found in MMA, with highest frequency in mut(0) patients. Unexpectedly, chronic renal failure was also observed in adolescent and adult patients with GA1 and ASL deficiency. It had a similar frequency in patients with or without a movement disorder suggesting different pathophysiology. Thirteen patients (classic OAD: 3, UCD: 10) died during the study interval, ten of them during the initial metabolic crisis in the newborn period. Male patients with late-onset ornithine transcarbamylase deficiency were presumably overrepresented in the study population.

CONCLUSIONS

Neurologic impairment is common in OAD and UCD, whereas the involvement of other organs (heart, liver, kidneys, eyes) follows a disease-specific pattern. The identification of unexpected chronic renal failure in GA1 and ASL deficiency emphasizes the importance of a systematic follow-up in patients with rare diseases.

Recommendations for the management of tyrosinaemia type 1

The management of tyrosinaemia type 1 (HT1, fumarylacetoacetase deficiency) has been revolutionised by the introduction of nitisinone but dietary treatment remains essential and the management is not easy. In this review detailed recommendations for the management are made based on expert opinion, published case reports and investigational studies as the evidence base is limited and there are no prospective controlled studies.The added value of this paper is that it summarises in detail current clinical knowledge about HT1 and makes recommendations for the management.

Clinical manifestations of Fabry disease in children: data from the Fabry Outcome Survey

BACKGROUND

Fabry disease is a rare X-linked disorder caused by deficient activity of the enzyme alpha-galactosidase A. This produces progressive lysosomal accumulation of globotriaosylceramide throughout the body, leading to organ failure and premature death.

AIM

Here, we present the clinical manifestations of Fabry disease in children enrolled in FOS--the Fabry Outcome Survey--a European database of the natural history of Fabry disease and the effects of enzyme replacement therapy with agalsidase alfa (Replagal).

METHODS

Currently, there are 545 patients in FOS, from 11 European countries. We analysed the baseline demographic and clinical characteristics of 82 of these patients (40 boys, 42 girls) who were below 18 y of age. The median age at evaluation (defined as the median age at entry into FOS) was 12.5 and 13.2 y for boys and girls, respectively.

RESULTS

The most frequent early clinical manifestations of Fabry disease were neurological (acroparaesthesiae, altered temperature sensitivity) and gastrointestinal symptoms (altered bowel habits and abdominal pain), which were documented in about 80% and 60% of patients, respectively, at the time of evaluation and subsequent entry into FOS. Tinnitus, vertigo, fatigue and angiokeratoma were present in over 40% of patients. Symptoms were noted in early childhood and occurred with similar frequency in boys and girls, although the onset of symptoms was 2-5 y later in girls than in boys. There was an approximately 3-y delay from onset of symptoms to diagnosis, and patients were frequently misdiagnosed.

CONCLUSION

Although the life-threatening complications of Fabry disease, such as stroke and renal and heart failure, are not seen in children, the present analysis shows that other symptoms are common and may have an impact on quality of life.

Fabry disease and the skin: data from FOS, the Fabry outcome survey

BACKGROUND

Fabry disease (also known as Anderson-Fabry disease) is a rare, X-linked lysosomal storage disorder that is characterized by accumulation of globotriaosylceramide throughout a range of tissues in the body.

OBJECTIVES

To ascertain the prevalence and nature of cutaneous manifestations in patients with Fabry disease and to relate these to the severity of systemic manifestations of the disease.

METHODS

We have documented the dermatological features of this disease with reference to data from 714 patients (345 males, 369 females) registered on the Fabry Outcome Survey (FOS), a multicentre European database.

RESULTS

We confirm that the commonest disease manifestation is angiokeratoma. Overall, 78% of males and 50% of females had one or more dermatological abnormality, the commonest being angiokeratoma (66% males, 36% females), hypohidrosis (53% males, 28% females), telangiectasia (23% males, 9% females) and lymphoedema (16% males, 6% females). We demonstrate for the first time that the presence of cutaneous vascular lesions correlates with the severity of the systemic manifestations of the disease (pain, renal failure, cardiac disease, premature cerebrovascular disease) as assessed by a severity scoring system. Although the condition is X linked, there is a surprisingly high prevalence of abnormalities in females.

CONCLUSIONS

The FOS database is a useful epidemiological tool in establishing the variety and relevance of cutaneous manifestations in Fabry disease. The present study confirms that the presence of dermatological manifestations appears to be a marker of greater severity of systemic disease, which emphasizes the importance of the dermatological assessment of these patients.

Long-term effectiveness of agalsidase alfa enzyme replacement in Fabry disease: A Fabry Outcome Survey analysis

Outcomes from 5 years of treatment with agalsidase alfa enzyme replacement therapy (ERT) for Fabry disease in patients enrolled in the Fabry Outcome Survey (FOS) were compared with published findings for untreated patients with Fabry disease. Data were extracted from FOS, a Shire-sponsored database, for comparison with data from three published studies. Outcomes evaluated were the annualized rate of change in estimated glomerular filtration rate (eGFR) and left ventricular mass indexed to height (LVMI) as well as time to and ages at a composite morbidity endpoint and at death. FOS data were extracted for 740 treated patients who were followed for a median of ~ 5 years. Compared with no treatment, patients treated with agalsidase alfa demonstrated slower decline in renal function and slower progression of left ventricular hypertrophy. Treated male patients with baseline eGFR < 60 mL/min/1.73 m² had a mean (standard error of the mean [SEM]) annualized change in eGFR of − 2.86 (0.53) mL/min/1.73 m²/y compared with − 6.8 (1.5) in the published untreated cohort. The mean (SEM) rate of LVMI increase with treatment was 0.33 (0.10) g/m^2.7/y in males and 0.48 (0.09) in females, compared with 4.07 (1.03) in untreated males and 2.31 (0.81) in untreated females. Morbidity occurred later in treated patients, with ~ 16% risk of a composite morbidity event (26% in males) after 24 months with ERT versus ~ 45% without treatment, with first events and deaths also occurring at older ages in patients administered ERT (e.g., estimated median survival in treated males was 77.5 years versus 60 years in untreated males). Findings from these retrospective comparisons of observational data and published literature support the long-term benefits of ERT with agalsidase alfa for Fabry disease in slowing the progression of renal impairment and cardiomyopathy. Treatment also appeared to delay the onset of morbidity and mortality. Interpretation of these findings should take into account that they are based on retrospective comparisons with previously published data.

Enzyme replacement therapy with agalsidase alfa in children with Fabry disease

AIM

To assess the effects of enzyme replacement therapy (ERT) in children with Fabry disease.

METHODS

Safety and efficacy of ERT with agalsidase alfa, 0.2 mg/kg infused over 40 minutes every 2 weeks for 23 weeks, were studied in a multicentre open-label trial in nine boys and four girls. Median age at the start of the study was 11.0 years (range 3.5-18 years).

RESULTS

Fifty-four adverse events were reported in 11 patients. No serious adverse events related to ERT were reported. Twelve of the 54 adverse events were considered possibly or probably related to ERT. Infusion reactions (8 mild, 3 moderate) occurred in four boys, in seven infusions. One boy developed IgG antibodies, although he continued to make good clinical progress. At the end of the study, two of the four boys and the one girl on regular pain medication at baseline had stopped taking analgesics. Brief Pain Inventory (BPI) scores decreased in most patients by week 12 and were sustained until the end of the study. This change was greater in the boys, who had higher (worse) BPI scores at baseline. Pain-related quality of life (QoL) scores also decreased during the study. Plasma globotriaosylceramide concentrations and urinary globotriaosylceramide:sphingomyelin ratios decreased after 12 and 23 weeks of therapy, particularly in the boys. Increases in sweat volume were recorded in three out of five of the boys and in one of two girls tested after 23 weeks of treatment.

CONCLUSION

ERT with agalsidase alfa in children with Fabry disease is well tolerated and, in the short term, appears to decrease pain and to improve pain-related QoL.

Genotypic and phenotypic features of all Spanish patients with McArdle disease: a 2016 update

BACKGROUND

We recently described the genotype/phenotype features of all Spanish patients diagnosed with McArdle disease as of January 2011 (n = 239, prevalence of ~1/167,000) (J Neurol Neurosurg Psychiatry 2012;83:322-8). Several caveats were however identified suggesting that the prevalence of the disease is actually higher.

METHODS

We have now updated main genotype/phenotype data, as well as potential associations within/between them, of all Spanish individuals currently diagnosed with McArdle disease (December 2016).

RESULTS

Ninety-four new patients (all Caucasian) have been diagnosed, yielding a prevalence of ~1/139,543 individuals. Around 55% of the mutated alleles have the commonest PYGM pathogenic mutation p.R50X, whereas p.W798R and p.G205S account for 10 and 9% of the allelic variants, respectively. Seven new mutations were identified: p.H35R, p.R70C, p.R94Q, p.L132WfsX163, p.Q176P, p.R576Q, and c.244-3_244-2CA. Almost all patients show exercise intolerance, the second wind phenomenon and high serum creatine kinase activity. There is, however, heterogeneity in clinical severity, with 8% of patients being asymptomatic during normal daily life, and 21% showing limitations during daily activities and fixed muscle weakness. A major remaining challenge is one of diagnosis, which is often delayed until the third decade of life in 72% of new patients despite the vast majority (86%) reporting symptoms before 20 years. An important development is the growing proportion of those reporting a 4-year improvement in disease severity (now 34%) and following an active lifestyle (50%). Physically active patients are more likely to report an improvement after a 4-year period in the clinical course of the disease than their inactive peers (odds ratio: 13.98; 95% confidence interval: 5.6, 34.9; p < 0.001). Peak oxygen uptake is also higher in the former (20.7 ± 6.0 vs. 16.8 ± 5.3 mL/kg/min, p = 0.0013). Finally, there is no association between PYGM genotype and phenotype manifestation of the disease.

CONCLUSIONS

The reported prevalence of McArdle disease grows exponentially despite frequent, long delays in genetic diagnosis, suggesting that many patients remain undiagnosed. Until a genetic cure is available (which is not predicted in the near future), current epidemiologic data support that adoption of an active lifestyle is the best medicine for these patients.

Fabry disease in children and the effects of enzyme replacement treatment

Fabry disease is a rare, X-linked inborn error of glycosphingolipid catabolism caused by a deficiency in the activity of the lysosomal enzyme, alpha-galactosidase A. In affected patients, the enzyme substrate, globotriaosylceramide (Gb3), accumulates in cells of various tissues and organs. Lysosomal accumulation of Gb3 begins in utero, and signs and symptoms of Fabry disease emerge in childhood and adolescence. The earliest presenting symptoms are typically neuropathic pain and gastrointestinal problems, which can have a substantial impact on health-related quality of life. Life-threatening major organ involvement is rare in young patients, but signs of kidney dysfunction (e.g., proteinuria), left ventricular hypertrophy, and stroke have been reported in children. There are two enzyme preparations for therapy: agalsidase alfa and beta. In two clinical trials of enzyme replacement therapy (ERT) with agalsidase alfa, including 37 children, boys demonstrated reductions in plasma Gb3 levels, and both boys and girls reported reductions in neuropathic pain and in the use of neuropathic pain medications. Heart rate variability, which is reduced in boys with Fabry disease, was statistically significantly improved with 6 months of agalsidase alfa treatment. In a single clinical study of agalsidase beta in children (n =16), skin Gb3 deposits and plasma Gb3 levels were reduced in boys. Differences exist in the administration and the safety profile of these two enzyme formulations. Follow-up of these cohorts and additional studies will be necessary to fully evaluate long-term efficacy of ERT in children with Fabry disease.

Twenty years of the Fabry Outcome Survey (FOS): insights, achievements, and lessons learned from a global patient registry

Background

Patient registries provide long-term, real-world evidence that aids the understanding of the natural history and progression of disease, and the effects of treatment on large patient populations with rare diseases. The year 2021 marks the 20th anniversary of the Fabry Outcome Survey (FOS), an international, multicenter, observational registry (NCT03289065). The primary aims of FOS are to broaden the understanding of Fabry disease (FD), an X-linked lysosomal storage disorder, and to improve the clinical management of affected patients. Here, we review the history of FOS and the analyses and publications disseminated from the registry, and we discuss the contributions FOS studies have made in understanding FD.

Results

FOS was initiated in April 2001 and, as of January 2021, 4484 patients with a confirmed diagnosis and patient informed consent have been enrolled from 144 centers across 26 countries. Data from FOS have been published in nearly 60 manuscripts on a wide variety of topics relevant to FD. Analyses of FOS data have investigated the long-term effectiveness and safety of enzyme replacement therapy (ERT) with agalsidase alfa and its effects on morbidity and mortality, as well as the benefits of prompt and early treatment with agalsidase alfa on the progression of cardiomyopathy and the decline in renal function associated with FD. Based on analyses of FOS data, ERT with agalsidase alfa has also been shown to improve additional signs and symptoms of FD experienced by patients. FOS data analyses have provided a better understanding of the natural history of FD and the specific populations of women, children, and the elderly, and have provided practical tools for the study of FD. FOS has also provided methodology and criteria for assessing disease severity which contributed to the continuous development of medical practice in FD and has largely improved our understanding of the challenges and needs of long-term data collection in rare diseases, aiding in future rare disease real-world evidence studies.

Conclusion

FOS over the last 20 years has substantially increased the scientific knowledge around improved patient management of FD and continues to expand our understanding of this rare disease.

First experience of enzyme replacement therapy with idursulfase in Spanish patients with Hunter syndrome under 5 years of age: case observations from the Hunter Outcome Survey (HOS)

Hunter syndrome (mucopolysaccharidosis type II [MPS II], OMIM309900) is a rare X-linked lysosomal storage disorder caused by deficiency of the enzyme iduronate-2-sulphatase, resulting in accumulation of glycosaminoglycans (GAGs), multisystem organ failure and early death. Enzyme replacement therapy (ERT) with idursulfase is commercially available since 2007. Early access programs were established since 2005. However, limited information on the effects of ERT in young children is available to date. The aim of this analysis was therefore to determine the effects of ERT on patients younger than 5 years of age. We report data from six Spanish patients with confirmed Hunter syndrome who were younger than 5 years at the start of ERT, and had been treated with weekly intravenous infusions of idursulfase between 6 and 14 months. Baseline and treatment data were obtained from the Hunter Outcome Survey (HOS). HOS is an international database of MPS II patients on ERT or candidates to be treated, that collects data in a registry manner. HOS is supported by Shire Human Genetic Therapies, Inc. (Cambridge, MA, USA). At baseline, all patients showed neurological abnormalities, including ventriculomegaly, hydrocephaly, cerebral atrophy, perivascular changes and white matter lesions. Other signs and symptoms included thoracic deformity, otitis media, joint stiffness and hepatosplenomegaly, demonstrating that children under 5 years old can also be severely affected. ERT reduced urinary GAG levels, and reduced spleen (n = 2) and liver size (n = 1) after only 8 months. Height growth was maintained within the normal range during ERT. Joint mobility either stabilized or improved during ERT. In conclusion, this case series confirms the early onset of signs and symptoms of Hunter syndrome and provides the first evidence of ERT beneficial effects in patients less than 5 years of age. Similar efficacy and safety profiles to those seen in older children can be suggested, although further studies including a direct comparison with older patients would still be required.

Tyrosinemia type 1 in Spain: mutational analysis, treatment and long-term outcome

BACKGROUND

Tyrosinemia type 1 (HT1) is a rare but treatable disease. The aim of the present study was to review the efficacy of long-term treatment of HT1 with nitisinone, expand knowledge about the clinical spectrum of the disease and assess a possible genotype-phenotype correlation.

METHODS

A retrospective multicenter study was carried out based on questionnaires on genotype, phenotype, therapy and outcome in 34 Spanish patients with HT1.

RESULTS

The main manifestations that led to the diagnosis were acute liver failure (55.8%), asymptomatic hepatomegaly (44.1%) and renal tubular dysfunction (29.4%). Laboratory analysis indicated a marked increase of α-fetoprotein and coagulopathy. The most common mutation was IVS6-1(G > T; 66.6% of 24/34 patients for whom mutation analysis was available) and these patients presented less nephrocalcinosis and more hepatomegaly at diagnosis; two novel mutations (c.974C>T, c.398A>T) were found. The mean duration of treatment was 6.73 years. Dietary compliance was very good in 47.1% and good in 20.6%; nitisinone treatment adherence was very good in 85.2% of cases. Mean dose of nitisinone was 0.87 mg/kg per day with average plasma levels of 45.67 µmol/L. Only one patient required liver transplantation after nitisinone and none had hepatocellular carcinoma.

CONCLUSIONS

Treatment with nitisinone has improved the prognosis of HT1, and compliance is good. In Spain, screening for HT1 by plasma tyrosine and urine succinylacetone determination may be implemented with IVS6-1(G > T) mutational analysis. A correlation between low frequency of nephrocalcinosis and IVS6-1(G > T) mutation was observed.

Urea cycle disorders in Spain: an observational, cross-sectional and multicentric study of 104 cases

BACKGROUND

Advances in the diagnosis and treatment of urea cycle disorders (UCDs) have led to a higher survival rate. The purpose of this study is to describe the characteristics of patients with urea cycle disorders in Spain.

METHODS

Observational, cross-sectional and multicenter study. Clinical, biochemical and genetic data were collected from patients with UCDs, treated in the metabolic diseases centers in Spain between February 2012 and February 2013, covering the entire Spanish population. Heterozygous mothers of patients with OTC deficiency were only included if they were on treatment due to being symptomatic or having biochemistry abnormalities.

RESULTS

104 patients from 98 families were included. Ornithine transcarbamylase deficiency was the most frequent condition (64.4%) (61.2% female) followed by type 1 citrullinemia (21.1%) and argininosuccinic aciduria (9.6%). Only 13 patients (12.5%) were diagnosed in a pre-symptomatic state. 63% of the cases presented with type intoxication encephalopathy. The median ammonia level at onset was 298 μmol/L (169-615). The genotype of 75 patients is known, with 18 new mutations having been described. During the data collection period four patients died, three of them in the early days of life. The median current age is 9.96 years (5.29-18), with 25 patients over 18 years of age. Anthropometric data, expressed as median and z-score for the Spanish population is shown. 52.5% of the cases present neurological sequelae, which have been linked to the type of disease, neonatal onset, hepatic failure at diagnosis and ammonia values at diagnosis. 93 patients are following a protein restrictive diet, 0.84 g/kg/day (0.67-1.10), 50 are receiving essential amino acid supplements, 0.25 g/kg/day (0.20-0.45), 58 arginine, 156 mg/kg/day (109-305) and 45 citrulline, 150 mg/kg/day (105-199). 65 patients are being treated with drugs: 4 with sodium benzoate, 50 with sodium phenylbutyrate, 10 with both drugs and 1 with carglumic acid.

CONCLUSIONS

Studies like this make it possible to analyze the frequency, natural history and clinical practices in the area of rare diseases, with the purpose of knowing the needs of the patients and thus planning their care.

Analysis of Renal and Cardiac Outcomes in Male Participants in the Fabry Outcome Survey Starting Agalsidase Alfa Enzyme Replacement Therapy Before and After 18 Years of Age

Purpose

To determine the impact of initiating enzyme replacement therapy (ERT) with agalsidase alfa early in the course of Fabry disease, we evaluated renal and cardiac outcomes for ≤10 years after ERT initiation in males from the Fabry Outcome Survey (FOS).

Patients and Methods

Male patients from FOS were stratified into three cohorts by age at ERT initiation: ≤18 years (cohort 1), >18 and ≤30 years (cohort 2), and >30 years (cohort 3). Analysis included age at symptom onset, diagnosis, and ERT initiation; ERT duration; FOS-Mainz Severity Score Index (FOS-MSSI); estimated glomerular filtration rate (eGFR); proteinuria level; and left ventricular mass indexed to height (LVMI). Mixed-effect models estimated renal and cardiac outcomes during follow-up between and within cohorts.

Findings

The analysis included 560 male patients: 151 (27.0%) in cohort 1, 155 (27.7%) in cohort 2, and 254 (45.4%) in cohort 3. Mean±SD duration of ERT for cohorts 1, 2, and 3 was 6.3±4.3, 8.6±4.9, and 7.9±4.9 years, respectively. Mean±SD baseline FOS-MSSI scores increased with age from 9.8±7.2 in cohort 1 to 24.7±11.4 in cohort 3. Cohort 3 showed the lowest baseline mean±SD value for eGFR (87.1±29.0 mL/min/1.73m²) and highest baseline mean±SD values for proteinuria (801.9±952.6 mg/day) and LVMI (56.7±16.0 g/m^2.7) among the three cohorts. Evaluation of mean annual rates of change in eGFR, proteinuria, and LVMI revealed no significant differences in any parameter for cohort 1. For cohort 2, proteinuria and LVMI remained stable, whereas eGFR significantly deteriorated annually (–1.12 mL/min/1.73m²; P<0.001). Cohort 3 demonstrated significant annual deteriorations in eGFR (–2.60 mL/min/1.73m²; P<0.001), proteinuria (+34.10 mg/day; P<0.001), and LVMI (+0.59 g/m^2.7; P=0.001).

Implications

Renal and/or cardiac disease progression appears attenuated in patients starting ERT in childhood or early adulthood versus patients starting ERT in later adulthood. These findings support early ERT initiation in Fabry disease. ClinicalTrials.gov identifier: NCT03289065.

Cardio- Renal Outcomes With Long- Term Agalsidase Alfa Enzyme Replacement Therapy: A 10- Year Fabry Outcome Survey (FOS) Analysis

Purpose

Following the publication of 5-year agalsidase alfa enzyme replacement therapy (ERT) outcomes data from the Fabry Outcome Survey (FOS), 10-year data were analyzed.

Patients and methods

FOS (ClinicalTrials.gov identifier: NCT03289065) data (April 2001 to August 2018) were retrospectively analyzed. Estimated glomerular filtration rate (eGFR) and left ventricular mass indexed to height (LVMI) were analyzed after treatment start (baseline) for patients with ≥3 measurements, including baseline and year 10.

Results

Median (range) age (years) of the evaluable treated renal cohort at treatment start was 48.8 (17.9–67.3) for females (n=62), 34.4 (18.0–66.8) for males (n=90). With eGFR ≥60 mL/min/1.73 m² at baseline, mean (95% CI) rate of eGFR change (eGFR/year) over 10 years was relatively stable in females (n=52; −0.55 [−1.12, +0.01]) and slightly declined in males (n=79; −1.99 [−2.45, −1.54]). With impaired kidney function (eGFR <60 mL/min/1.73 m²) at baseline, mean (95% CI) eGFR/year was stable in females (n=10; −0.14 [−1.43, +1.15]) and slightly declined in males (n=11; −2.79 [−4.01, −1.56]) over 10 years. Median (range) age (years) of the evaluable treated cardiac cohort at treatment start was 46.7 (3.7–67.3) for females (n=34), 28.2 (4.0–54.2) for males (n=35). With left ventricular hypertrophy (LVH; LVMI >48 g/m^2.7 in females, >50 g/m^2.7 in males) at baseline, mean (95% CI) LVMI/year slightly increased over 10 years in females (n=18; +1.51 [+0.91, +2.12]) and males (n=14; +0.87 (+0.19, +1.55). Without LVH at baseline, mean (95% CI) LVMI/year was stable in females (n=16; +0.52 [−0.13, +1.17]) and males (n=21; +0.57 [+0.02, +1.13]) over 10 years.

Conclusion

Agalsidase alfa-treated patients with 10-year FOS data and preserved kidney function and/or normal LVMI at baseline remained largely stable; those with decreased kidney function or LVH at baseline experienced modest declines in renal function and/or increases in LVMI.

Severe cardiac phenotype of Berardinelli-Seip congenital lipodystrophy in an infant with homozygous E189X BSCL2 mutation

Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare autosomal recessive condition associating insulin resistance, absence of subcutaneous fat and muscular hypertrophy. Disease-causing mutations have been described in AGPAT2 and BSCL2 genes. Hypertrophic cardiomyopathy is a classical late (third decade) complication which has only been occasionally described in childhood. We report on a 4-month-old Chinese male infant who presented with a severe BSCL "cardiac" phenotype comprising heart failure, hypertension and hypertrophic cardiomyopathy.

Rare Neurodegenerative Diseases: Clinical and Genetic Update

More than 600 human disorders afflict the nervous system. Of these, neurodegenerative diseases are usually characterised by onset in late adulthood, progressive clinical course, and neuronal loss with regional specificity in the central nervous system. They include Alzheimer's disease and other less frequent dementias, brain cancer, degenerative nerve diseases, encephalitis, epilepsy, genetic brain disorders, head and brain malformations, hydrocephalus, stroke, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis (ALS or Lou Gehrig's Disease), Huntington's disease, and Prion diseases, among others. Neurodegeneration usually affects, but is not limited to, the cerebral cortex, intracranial white matter, basal ganglia, thalamus, hypothalamus, brain stem, and cerebellum. Although the majority of neurodegenerative diseases are sporadic, Mendelian inheritance is well documented. Intriguingly, the clinical presentations and neuropathological findings in inherited neurodegenerative forms are often indistinguishable from those of sporadic cases, suggesting that converging genomic signatures and pathophysiologic mechanisms underlie both hereditary and sporadic neurodegenerative diseases. Unfortunately, effective therapies for these diseases are scarce to non-existent. In this chapter, we highlight the clinical and genetic features associated with the rare inherited forms of neurodegenerative diseases, including ataxias, multiple system atrophy, spastic paraplegias, Parkinson's disease, dementias, motor neuron diseases, and rare metabolic disorders.

A DM1 family with interruptions associated with atypical symptoms and late onset but not with a milder phenotype

Carriage of interruptions in CTG repeats of the myotonic dystrophy protein kinase gene has been associated with a broad spectrum of myotonic dystrophy type 1 (DM1) phenotypes, mostly mild. However, the data available on interrupted DM1 patients and their phenotype are scarce. We studied 49 Spanish DM1 patients, whose clinical phenotype was evaluated in depth. Blood DNA was obtained and analyzed through triplet-primed polymerase chain reaction (PCR), long PCR-Southern blot, small pool PCR, AciI digestion, and sequencing. Five patients of our registry (10%), belonging to the same family, carried CCG interruptions at the 3'-end of the CTG expansion. Some of them presented atypical traits such as very late onset of symptoms ( > 50 years) and a severe axial and proximal weakness requiring walking assistance. They also showed classic DM1 symptoms including cardiac and respiratory dysfunction, which were severe in some of them. Sizes and interrupted allele patterns were determined, and we found a contraction and an expansion in two intergenerational transmissions. Our study contributes to the observation that DM1 patients carrying interruptions present with atypical clinical features that can make DM1 diagnosis difficult, with a later than expected age of onset and a previously unreported aging-related severe disease manifestation.

Fabry disease in Spain: description of Spanish patients and a comparison with other European countries using data from the Fabry Outcome Survey (FOS)

AIMS

Fabry disease (FD) is an X-chromosome-linked transmitted lysosomal storage disorder as a result of the deficient activity of enzyme α-galactosidase A. This leads to accumulation of neutral glycosphingolipids associated with organ involvement and premature death. We report the clinical characteristics of Spanish patients enrolled on the Fabry Outcome Survey (FOS; an international multicentre registry for the disease) and also compare these data with those from the rest of Europe.

METHODS

Baseline clinical data of 92 patients (41 males and 51 females) are described and analysed globally and according to gender. We compare the data of Spanish patients with those previously published from the rest of Europe patients in FOS.

RESULTS

Mean age of onset of symptoms in men was 20, and 24 years in women, with a mean delay of 11 years to the diagnosis in both genders. The predominant clinical involvement in male patients was renal (69%), cardiac (66%) and neurological (60%), and for female patients, it was neurological (42%), cardiac (33%), keratopathy (30%) and nephropathy (28%). Disease severity was significantly higher in male patients. Compared to the rest of European FOS-patients, Spanish patients were diagnosed at an earlier age with a smaller proportion of disease-related involvement for most organ irrespective of gender, though not its global severity in male patients.

CONCLUSIONS

We present the largest cohort of Spanish patients diagnosed with FD. The pattern of involvement (though not its global severity) could be different in Spanish patients in comparison with others from Europe. Expanding the knowledge of FD will permit early diagnosis as well as the possibility of starting the specific treatment.

Missense mutations have unexpected consequences: The McArdle disease paradigm

McArdle disease is a disorder of muscle glycogen metabolism caused by mutations in the PYGM gene, encoding for the muscle-specific isoform of glycogen phosphorylase (M-GP). The activity of this enzyme is completely lost in patients' muscle biopsies, when measured with a standard biochemical test which, does not allow to determine M-GP protein levels. We aimed to determine M-GP protein levels in the muscle of McArdle patients, by studying biopsies of 40 patients harboring a broad spectrum of PYGM mutations and 22 controls. Lack of M-GP protein was found in muscle in the vast majority (95%) of patients, irrespective of the PYGM genotype, including those carrying missense mutations, with few exceptions. M-GP protein biosynthesis is not being produced by PYGM mutations inducing premature termination codons (PTC), neither by most PYGM missense mutations. These findings explain the lack of PYGM genotype-phenotype correlation and have important implications for the design of molecular-based therapeutic approaches.

A novel nonstop mutation in TYMP does not induce nonstop mRNA decay in a MNGIE patient with severe neuropathy

The cellular quality control systems enable surveillance and selective degradation of nonsense, nonstop, and no-go mRNAs. In the case of nonstop mRNA, different mechanisms of nonstop-mediated decay (NSD) have been described for bacteria, yeast and mammals, but the molecular consequences of nonstop mutations have been examined in only few cases of human disease. We describe a novel homozygous nonstop mRNA mutation (c.1416delC) in the TYMP gene encoding thymidine phosphorylase, in a patient with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). In contrast to previous reports showing selective decay of pathogenic nonstop mRNAs, quantitative real-time PCR and 3'-RACE-RFLP analysis revealed unreduced nonstop mRNA levels in our patient and 2 heterozygous carriers of the mutation. The absence of thymidine phosphorylase protein in the homozygous patient, together with the partial decrease in levels of this protein in 2 carriers suggest that the main control system in this case resides at the translational or post-translational levels rather than through NSD. This is the first report showing an absence of NSD in a human disease, revealing that this surveillance mechanism has exceptions in vivo.

Biomarkers in Fabry Disease. Implications for Clinical Diagnosis and Follow-up

Fabry disease (FD) is a lysosomal storage disorder caused by deficient alpha-galactosidase A activity in the lysosome due to mutations in the GLA gene, resulting in gradual accumulation of globotriaosylceramide and other derivatives in different tissues. Substrate accumulation promotes different pathogenic mechanisms in which several mediators could be implicated, inducing multiorgan lesions, mainly in the kidney, heart and nervous system, resulting in clinical manifestations of the disease. Enzyme replacement therapy was shown to delay disease progression, mainly if initiated early. However, a diagnosis in the early stages represents a clinical challenge, especially in patients with a non-classic phenotype, which prompts the search for biomarkers that help detect and predict the evolution of the disease. We have reviewed the mediators involved in different pathogenic mechanisms that were studied as potential biomarkers and can be easily incorporated into clinical practice. Some accumulation biomarkers seem to be useful to detect non-classic forms of the disease and could even improve diagnosis of female patients. The combination of such biomarkers with some response biomarkers, may be useful for early detection of organ injury. The incorporation of some biomarkers into clinical practice may increase the capacity of detection compared to that currently obtained with the established diagnostic markers and provide more information on the progression and prognosis of the disease.

Genes and exercise intolerance: insights from McArdle disease

McArdle disease (glycogen storage disease type V) is caused by inherited deficiency of a key enzyme in muscle metabolism, the skeletal muscle-specific isoform of glycogen phosphorylase, “myophosphorylase,” which is encoded by the PYGM gene. Here we review the main pathophysiological, genotypic, and phenotypic features of McArdle disease and their interactions. To date, moderate-intensity exercise (together with pre-exercise carbohydrate ingestion) is the only treatment option that has proven useful for these patients. Furthermore, regular physical activity attenuates the clinical severity of McArdle disease. This is quite remarkable for a monogenic disorder that consistently leads to the same metabolic defect at the muscle tissue level, that is, complete inability to use muscle glycogen stores. Further knowledge of this disorder would help patients and enhance understanding of exercise metabolism as well as exercise genomics. Indeed, McArdle disease is a paradigm of human exercise intolerance and PYGM genotyping should be included in the genetic analyses that might be applied in the coming personalized exercise medicine as well as in future research on genetics and exercise-related phenotypes.