Prevalence of DDC genotypes in patients with aromatic L-amino acid decarboxylase (AADC) deficiency and in silico prediction of structural protein changes.

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare autosomal recessive genetic disorder affecting the biosynthesis of dopamine, a precursor of both norepinephrine and epinephrine, and serotonin. Diagnosis is based on the analysis of CSF or plasma metabolites, AADC activity in plasma and genetic testing for variants in the DDC gene. The exact prevalence of AADC deficiency, the number of patients, and the variant and genotype prevalence are not known. Here, we present the DDC variant (n = 143) and genotype (n = 151) prevalence of 348 patients with AADC deficiency, 121 of whom were previously not reported. In addition, we report 26 new DDC variants, classify them according to the ACMG/AMP/ACGS recommendations for pathogenicity and score them based on the predicted structural effect. The splice variant c.714+4A>T, with a founder effect in Taiwan and China, was the most common variant (allele frequency = 32.4%), and c.[714+4A>T];[714+4A>T] was the most common genotype (genotype frequency = 21.3%). Approximately 90% of genotypes had variants classified as pathogenic or likely pathogenic, while 7% had one VUS allele and 3% had two VUS alleles. Only one benign variant was reported. Homozygous and compound heterozygous genotypes were interpreted in terms of AADC protein and categorized as: i) devoid of full-length AADC, ii) bearing one type of AADC homodimeric variant or iii) producing an AADC protein population composed of two homodimeric and one heterodimeric variant. Based on structural features, a score was attributed for all homodimers, and a tentative prediction was advanced for the heterodimer. Almost all AADC protein variants were pathogenic or likely pathogenic.

Consensus Recommendations for the Clinical Management of Hematological Malignancies in Patients with DNA Double Stranded Break Disorders.

Patients with double stranded DNA repair disorders (DNARDs) (Ataxia Telangiectasia (AT) and Nijmegen Breakage syndrome (NBS)) are at a very high risk for developing hematological malignancies in the first two decades of life. The most common neoplasms are T-cell lymphoblastic malignancies (T-cell ALL and T-cell LBL) and diffuse large B cell lymphoma (DLBCL). Treatment of these patients is challenging due to severe complications of the repair disorder itself (e.g., congenital defects, progressive movement disorders, immunological disturbances and progressive lung disease) and excessive toxicity resulting from chemotherapeutic treatment. Frequent complications during treatment for malignancies are deterioration of pre-existing lung disease, neurological complications, severe mucositis, life threating infections and feeding difficulties leading to significant malnutrition. These complications make modifications to commonly used treatment protocols necessary in almost all patients. Considering the rarity of DNARDs it is difficult for individual physicians to obtain sufficient experience in treating these vulnerable patients. Therefore, a team of experts assembled all available knowledge and translated this information into best available evidence-based treatment recommendations.

Insights into the expanding phenotypic spectrum of inherited disorders of biogenic amines.

Inherited disorders of neurotransmitter metabolism are rare neurodevelopmental diseases presenting with movement disorders and global developmental delay. This study presents the results of the first standardized deep phenotyping approach and describes the clinical and biochemical presentation at disease onset as well as diagnostic approaches of 275 patients from the registry of the International Working Group on Neurotransmitter related Disorders. The results reveal an increased rate of prematurity, a high risk for being small for gestational age and for congenital microcephaly in some disorders. Age at diagnosis and the diagnostic delay are influenced by the diagnostic methods applied and by disease-specific symptoms. The timepoint of investigation was also a significant factor: delay to diagnosis has decreased in recent years, possibly due to novel diagnostic approaches or raised awareness. Although each disorder has a specific biochemical pattern, we observed confounding exceptions to the rule. The data provide comprehensive insights into the phenotypic spectrum of neurotransmitter disorders.

Hypocalcemia as a Cause of Complex Febrile Seizures in a Toddler.

A 13-month-old boy had suffered three episodes of complex febrile seizures. At this admission, there were signs of hyperexcitability, such as Trousseau sign and QTc prolongation. A point of care blood gas analysis revealed severe hypocalcemia. Therefore, prior to administering intravenous calcium gluconate, we took blood samples to investigate the etiology of this hypocalcemia: magnesium, parathormone, and 25-hydroxyvitamin D. Since both parathormone and phosphate were significantly elevated and 25-hydroxyvitamin D was within the normal range, pseudohypoparathyroidism was diagnosed. After two years of follow-up, serum calcium had normalized in our patient under supplementation of vitamin D and calcium. He had been free of convulsions, although different febrile episodes had occurred.

Blood, urine and cerebrospinal fluid analysis in TH and AADC deficiency and the effect of treatment.

BACKGROUND: Aromatic L-amino acid decarboxylase (AADC) deficiency and tyrosine hydroxylase (TH) deficiency are rare inherited disorders of monoamine neurotransmitter synthesis which are typically diagnosed using cerebrospinal fluid examination of monoamine neurotransmitter metabolites. Until now, it has not been systematically studied whether analysis of monamine neurotransmitter metabolites in blood or urine has diagnostic value as compared to cerebrospinal fluid examination, or whether monoamine neurotransmitter metabolites in these peripheral body fluids is useful to monitor treatment efficacy. METHODS: Assessment, both by literature review and retrospective analysis of our local university hospital database, of monoamine neurotransmitter metabolites in urine, blood and cerebrospinal fluid, and serum prolactin levels, before and during treatment in patients with AADC and TH deficiency. RESULTS: In AADC deficiency, 3-O-methyldopa in serum or dried blood spots was reported in 34 patients and found to be (strongly) increased in all, serotonin in serum was decreased in 7/7 patients. Serum prolactin was increased in 34/37 and normal in 3 untreated patients. In urine, dopamine was normal or increased in 21/24 patients, 5-hydroxyindoleacetic acid was decreased in 9/10 patients, and vanillactic acid was increased in 19/20 patients. No significant changes were seen in monoamine neurotransmitter metabolites after medical treatment, except for an increase of homovanillic acid in urine and cerebrospinal fluid after levodopa therapy, sometimes even in absence of a clinical response. After gene therapy, cerebrospinal fluid homovanillic acid increased in most patients (8/12), but 5-hydroxyindoleacetic acid remained unchanged in 9/12 patients.In TH deficiency, serum prolactin was increased in 12/14 and normal in the remaining untreated patients. Urinary dopamine was decreased in 2/8 patients and normal in 6. Homovanillic acid concentrations in cerebrospinal fluid increased upon levodopa treatment, even in the absence of a clear treatment response. CONCLUSIONS: This study confirms that cerebrospinal fluid is the most informative body fluid to measure monoamine neurotransmitter metabolites when AADC or TH deficiency is suspected, and that routine follow-up of cerebrospinal fluid measurements to estimate treatment response is not needed. 3-O-methyldopa in dried blood spots and vanillactic acid in urine are promising peripheral biomarkers for diagnosis of AADC deficiency. However, in many patients with TH or AADC deficiency dopamine in urine is normal or increased thereby not reflecting the metabolic block. The value of serum prolactin for follow-up of AADC and TH deficiency should be further studied.

Novel Protein Biomarkers of Monoamine Metabolism Defects Correlate with Disease Severity.

BACKGROUND: Genetic defects of monoamine neurotransmitters are rare neurological diseases amenable to treatment with variable response. They are major causes of early parkinsonism and other spectrum of movement disorders including dopa-responsive dystonia. OBJECTIVES: The objective of this study was to conduct proteomic studies in cerebrospinal fluid (CSF) samples of patients with monoamine defects to detect biomarkers involved in pathophysiology, clinical phenotypes, and treatment response. METHODS: A total of 90 patients from diverse centers of the International Working Group on Neurotransmitter Related Disorders were included in the study (37 untreated before CSF collection, 48 treated and 5 unknown at the collection time). Clinical and molecular metadata were related to the protein abundances in the CSF. RESULTS: Concentrations of 4 proteins were significantly altered, detected by mass spectrometry, and confirmed by immunoassays. First, decreased levels of apolipoprotein D were found in severe cases of aromatic L-amino acid decarboxylase deficiency. Second, low levels of apolipoprotein H were observed in patients with the severe phenotype of tyrosine hydroxylase deficiency, whereas increased concentrations of oligodendrocyte myelin glycoprotein were found in the same subset of patients with tyrosine hydroxylase deficiency. Third, decreased levels of collagen6A3 were observed in treated patients with tetrahydrobiopterin deficiency. CONCLUSION: This study with the largest cohort of patients with monoamine defects studied so far reports the proteomic characterization of CSF and identifies 4 novel biomarkers that bring new insights into the consequences of early dopaminergic deprivation in the developing brain. They open new possibilities to understand their role in the pathophysiology of these disorders, and they may serve as potential predictors of disease severity and therapies. © 2020 International Parkinson and Movement Disorder Society.

Clinical presentation and long-term follow-up of dopamine beta hydroxylase deficiency.

Dopamine beta hydroxylase (DBH) deficiency is an extremely rare autosomal recessive disorder with severe orthostatic hypotension, that can be treated with L-threo-3,4-dihydroxyphenylserine (L-DOPS). We aimed to summarize clinical, biochemical, and genetic data of all world-wide reported patients with DBH-deficiency, and to present detailed new data on long-term follow-up of a relatively large Dutch cohort. We retrospectively describe 10 patients from a Dutch cohort and 15 additional patients from the literature. We identified 25 patients (15 females) from 20 families. Ten patients were diagnosed in the Netherlands. Duration of follow-up of Dutch patients ranged from 1 to 21 years (median 13 years). All patients had severe orthostatic hypotension. Severely decreased or absent (nor)epinephrine, and increased dopamine plasma concentrations were found in 24/25 patients. Impaired kidney function and anemia were present in all Dutch patients, hypomagnesaemia in 5 out of 10. Clinically, all patients responded very well to L-DOPS, with marked reduction of orthostatic complaints. However, orthostatic hypotension remained present, and kidney function, anemia, and hypomagnesaemia only partially improved. Plasma norepinephrine increased and became detectable, while epinephrine remained undetectable in most patients. We confirm the core clinical characteristics of DBH-deficiency and the pathognomonic profile of catecholamines in body fluids. Impaired renal function, anemia, and hypomagnesaemia can be part of the clinical presentation. The subjective response to L-DOPS treatment is excellent and sustained, although the neurotransmitter profile in plasma does not normalize completely. Furthermore, orthostatic hypotension as well as renal function, anemia, and hypomagnesaemia improve only partially.

Correction to: Consensus guideline for the diagnosis and treatment of tetrahydrobiopterin (BH4) deficiencies.

An amendment to this paper has been published and can be accessed via the original article.

Consensus guideline for the diagnosis and treatment of tetrahydrobiopterin (BH4) deficiencies.

BACKGROUND: Tetrahydrobiopterin (BH4) deficiencies comprise a group of six rare neurometabolic disorders characterized by insufficient synthesis of the monoamine neurotransmitters dopamine and serotonin due to a disturbance of BH4 biosynthesis or recycling. Hyperphenylalaninemia (HPA) is the first diagnostic hallmark for most BH4 deficiencies, apart from autosomal dominant guanosine triphosphate cyclohydrolase I deficiency and sepiapterin reductase deficiency. Early supplementation of neurotransmitter precursors and where appropriate, treatment of HPA results in significant improvement of motor and cognitive function. Management approaches differ across the world and therefore these guidelines have been developed aiming to harmonize and optimize patient care. Representatives of the International Working Group on Neurotransmitter related Disorders (iNTD) developed the guidelines according to the SIGN (Scottish Intercollegiate Guidelines Network) methodology by evaluating all available evidence for the diagnosis and treatment of BH4 deficiencies. CONCLUSION: Although the total body of evidence in the literature was mainly rated as low or very low, these consensus guidelines will help to harmonize clinical practice and to standardize and improve care for BH4 deficient patients.

Autosomal dominant GCH1 mutations causing spastic paraplegia at disease onset.

BACKGROUND: Autosomal dominant GCH1 mutations are known to cause dopa-responsive dystonia (DRD). In this case series, we confirm a variant phenotype, characterized by predominant spastic paraplegia at disease onset with development of dystonia and/or parkinsonism only decades later. METHODS: Clinical trajectories of four patients from three families with pathogenic variants in GCH1 are described, illustrated by videos of the motor phenotype before and during treatment with levodopa. An extensive literature review was performed on previous reports of spasticity in patients with autosomal dominant GCH1 mutations. RESULTS: All patients presented during childhood or early adolescence with gait and leg spasticity. Three patients developed basal ganglia signs only in the fifth decade; the youngest patient has not yet developed dystonia, bradykinesia or hypokinesia. All patients responded to levodopa/carbidopa with improvement of gait and of dystonia, hypokinesia and/or rigidity. In all patients, spasticity decreased but did not disappear. Spasticity has been described previously in DRD, but in most cases co-existent basal ganglia signs were identified early in the disease course. CONCLUSION: GCH1 mutations may cause a phenotype initially resembling hereditary spastic paraplegia (HSP) rather than DRD, with basal ganglia signs developing only after decades. In order not to miss this treatable condition, GCH1 should be included in HSP gene panels and its testing is pivotal in patients with spastic paraplegia, especially if there are concomitant basal ganglia signs and/or diurnal fluctuation.

CAPN1 mutations: Expanding the CAPN1-related phenotype: From hereditary spastic paraparesis to spastic ataxia.

AIMS AND OBJECTIVE: To characterize the phenotype of CAPN1 (SPG76) mutations in patients diagnosed with hereditary spastic paraplegia (HSP). BACKGROUND: The CAPN1 gene, located on chromosome 11q13.1, is a protein-coding gene involved in neuronal plasticity, migration, microtubular regulation and cerebellar development. Several families with CAPN1 mutations have recently been reported to present with autosomal recessive (AR) HSP and/or ataxia. METHOD: Patients with HSP were identified through neurological and genetic clinics with detailed phenotyping. Whole exome sequencing revealed novel pathogenic CAPN1 mutations in four patients from 3 families. RESULTS: Affected families were of Turkish, Japanese, and Punjabi descent and all were consanguineous. Onset of spastic paraplegia in the four patients was between 20 and 37 years. Two also had mild ataxia. Three different novel, homozygous mutations in CAPN1 were found: c.2118+1G > T, c.397C > T, c.843+1G > C. The patient with the earliest onset also manifested profound muscle weakness, likely related to a second homozygous mutation in DYSF (dysferlinopathy). CONCLUSIONS: The phenotype of AR CAPN1 mutations appears to be spastic paraplegia with or without ataxia; onset is most commonly in adulthood. Eye movement abnormalities, skeletal defects, peripheral neuropathy and amyotrophy can sometimes be seen. Occasionally, patients can present with ataxia, illustrating the genotypic and phenotypic overlap between HSP and spastic ataxia. With the advent of exome sequencing, mutations in more than one gene can be identified, which may contribute to the phenotypic variation, even within a family.

l-Dopa in dystonia: A modern perspective.

"Every child exhibiting dystonia merits an l-dopa trial, lest the potentially treatable condition of dopa-responsive dystonia (DRD) is missed" has been a commonly cited and highly conserved adage in movement disorders literature stemming from the 1980s. We here provide a historical perspective on this statement, discuss the current diagnostic and therapeutic applications of l-dopa in everyday neurologic practice, contrast these with its approved indications, and finish with our view on both a diagnostic and therapeutic trial in children and adults with dystonia. In light of the relatively low prevalence of DRDs, the large interindividual variation in the required l-dopa dose, the uncertainty about an adequate trial duration, the substantial advances in knowledge on etiology and pathophysiology of these disorders, and the availability of various state-of-the-art diagnostic tests, we think that a diagnostic l-dopa trial as a first step in the approach of early-onset dystonia (≤25 years) is outdated. Rather, in high-resource countries, we suggest to use l-dopa after biochemical corroboration of a defect in dopamine biosynthesis, in genetically confirmed DRD, or if nigrostriatal degeneration has been demonstrated by nuclear imaging in adult patients presenting with lower limb dystonia. Furthermore, our literature study on the effect of a therapeutic trial to gain symptomatic relief revealed that l-dopa has occasionally proven beneficial in several established "non-DRDs" and may therefore be considered in selected cases of dystonia due to other causes. In summary, we argue against the application of l-dopa in every patient with early-onset dystonia and support a more rational therapeutic use.

Consensus guideline for the diagnosis and treatment of aromatic l-amino acid decarboxylase (AADC) deficiency.

Aromatic L-amino acid decarboxylase deficiency (AADCD) is a rare, autosomal recessive neurometabolic disorder that leads to a severe combined deficiency of serotonin, dopamine, norepinephrine and epinephrine. Onset is early in life, and key clinical symptoms are hypotonia, movement disorders (oculogyric crisis, dystonia, and hypokinesia), developmental delay, and autonomic symptoms.In this consensus guideline, representatives of the International Working Group on Neurotransmitter Related Disorders (iNTD) and patient representatives evaluated all available evidence for diagnosis and treatment of AADCD and made recommendations using SIGN and GRADE methodology. In the face of limited definitive evidence, we constructed practical recommendations on clinical diagnosis, laboratory diagnosis, imaging and electroencephalograpy, medical treatments and non-medical treatments. Furthermore, we identified topics for further research. We believe this guideline will improve the care for AADCD patients around the world whilst promoting general awareness of this rare disease.

The International Working Group on Neurotransmitter related Disorders (iNTD): A worldwide research project focused on primary and secondary neurotransmitter disorders.

INTRODUCTION: Neurotransmitters are chemical messengers that enable communication between the neurons in the synaptic cleft. Inborn errors of neurotransmitter biosynthesis, breakdown and transport are a group of very rare neurometabolic diseases resulting in neurological impairment at any age from newborn to adulthood. METHODS AND RESULTS: The International Working Group on Neurotransmitter related Disorders (iNTD) is the first international network focusing on the study of primary and secondary neurotransmitter disorders. It was founded with the aim to foster exchange and improve knowledge in the field of these rare diseases. The newly established iNTD patient registry for neurotransmitter related diseases collects longitudinal data on the natural disease course, approach to diagnosis, therapeutic strategies, and quality of life of affected patients. The registry forms the evidence base for the development of consensus guidelines for patients with neurotransmitter related disorders. CONCLUSION: The iNTD network and registry will improve knowledge and strengthen research capacities in the field of inborn neurotransmitter disorders. The evidence-based guidelines will facilitate standardized diagnostic procedures and treatment approaches.

The paradox of hyperdopaminuria in aromatic L-amino Acid deficiency explained.

Aromatic L-amino acid decarboxylase (AADC) decarboxylates 3,4-L-dihydroxylphenylalanine (L-dopa) to dopamine, and 5-hydroxytryptophan to serotonin. In AADC deficiency, dopamine and serotonin deficiency leads to a severe clinical picture with mental retardation, oculogyric crises, hypotonia, dystonia, and autonomic dysregulation. However, despite dopamine deficiency in the central nervous system, urinary dopamine excretion in AADC-deficient patients is normal to high.In human, renal AADC-activity is very high compared to other tissues including brain tissue. Plasma L-dopa levels are increased in AADC deficiency. In this study, the hypothesis that in AADC deficiency relatively high-residual renal AADC-activity combined with high substrate availability of L-dopa leads to normal or elevated levels of urinary dopamine is tested and verified using 24-h urine collection of two AADC-deficient patients.Renal dopamine is a major regulator of natriuresis and plays a crucial role in the maintenance of sodium homeostasis. Therefore, the preservation of sufficient renal AADC-activity in AADC deficiency might be crucial for survival of AADC-deficient patients.In this study, we underpinned an empirical finding with theory, thereby putting a clinical observation into its physiological context. Our study stresses the difference - not qualitatively but quantitatively - between dopamine production in the central nervous system and peripheral organs. Furthermore, this study clarifies the so far unexplained observation that neurotransmitter profiles in urine should be interpreted with extreme caution in the diagnostic work-up of patients suspected to suffer from neurometabolic disorders.

Multi-channel amplitude-integrated EEG characteristics in preterm infants with a normal neurodevelopment at two years of corrected age.

AIM: To analyze quantitatively multi-channel amplitude-integrated EEG (aEEG) characteristics and assess regional differences. METHODS: We investigated 40 preterm infants (postmenstrual age, PMA: range 27-37 weeks) with normal follow-up at 24 months of age, at a median postnatal age of 8 days using 4-h EEG recordings according to the international 10-20 system reduced montage. Nine (3 transverse and 6 longitudinal) channels were selected and converted to aEEG registrations. For each aEEG registration, lower margin amplitude (LMA), upper margin amplitude (UMA) and bandwidth (UMA-LMA) were calculated. RESULTS: In all channels PMA and LMA showed strong positive correlations. Below 32 weeks of PMA, LMA was ≤5µV. Linear regression analysis showed a maximum LMA difference between channels of approximately 2 and 1µV at 27 and 37 weeks of PMA, respectively. The lowest are LMA values in the occipital channel and the highest values are in centro-occipital channels. In the frontal, centro-temporal and centro-occipital channels, UMA and bandwidth changed with PMA. No differences in LMA, UMA and bandwidth were found between hemispheres. Skewness of LMA values strongly correlated with PMA, positive skewness indicating an immature brain (PMA≤32 weeks) and negative skewness a maturing (PMA>32 weeks) brain. CONCLUSIONS: We detected symmetric increase of aEEG characteristics, indicating symmetric brain maturation of the left and right hemispheres. Our findings demonstrate the clinical potential of computer-assisted analyses of aEEG recordings in detecting maturational features which are not readily identified visually. This may provide an objective and reproducible method for assessing brain maturation and long-term prognosis.

Neurodevelopmental outcome in full-term newborns with refractory neonatal seizures.

AIM: This retrospective study describes the prognosis of full-term newborns with refractory neonatal seizures, comparing the need for treatment with two versus three or more antiepileptic drugs. METHODS: We reviewed our database (January 2002-December 2007) to include newborns with refractory neonatal seizures and abnormal electroencephalogram. Group A consisted of 17 newborns with two antiepileptic drugs. Group B consisted of 29 newborns with three or more antiepileptic drugs. Outcome was determined at 2 years of age using the Dutch Bayley Scales of Infant Development or a neurodevelopmental classification scheme. RESULTS: Group A and group B were comparable regarding to a variety of demographic and aetiologic factors. Thirteen newborns died before 2 years of age and one was lost to follow-up. Normal development at 2 years of age was found in 50% and 5% for group A and B, respectively. Severe neurodevelopmental delay at 2 years of age was found in 30% and 68% for group A and B, respectively. CONCLUSION: The number of antiepileptic drugs probably reflects increased seizure burden and is--in that way--related to poor outcome. This may be useful information for early prediction of adverse neurological outcome in the first days of life.