Yasmina Amraoui

Niemann-Pick disease type C clinical database: cognitive and coordination deficits are early disease indicators

BackgroundThe neurodegenerative lysosomal storage disorder Niemann-Pick disease type C (NP-C) is characterized by a broad clinical variability involving neurological, psychiatric and systemic signs. Diverse patterns of disease manifestation and progression considerably delay its diagnosis. Here we introduce the NP-C clinical database (NPC-cdb) to systematically obtain, store and analyze diagnostic and clinical findings in patients with NP-C. We apply NPC-cdb to study NP-C temporal expression in a large German-Swiss patient cohort.MethodsCurrent and past medical history was systematically acquired from 42 patients using tailored questionnaires. Manifestation of 72 distinct neuropsychiatric signs was modeled over the course of disease. The sequence of disease progression was re-constructed by a novel clinical outcome scale (NPC-cdb score).ResultsThe efficiency of current clinical diagnostic standards negatively correlates with duration of disease (p<3.9x10-4), suggesting insufficient sensitivity in patients early in the disease process. Neurological signs considered as typical for NP-C were frequent (e.g., cognitive impairment 86%, ataxia 79%, vertical supranuclear gaze palsy 76%) and their presence co-occurred with accelerated diagnosis. However, less specific neuropsychiatric signs were reported to arise considerably more early in the disease process (e.g., clumsiness -4.9±1.1 y before diagnosis). Most patients showed a steady disease progression that correlated with age at neurological onset. However, a distinct subcohort (n=6) with initially steadily progressing disease later showed a 2.9-fold accelerated progression that was associated with the onset of seizures (p<7x10-4), suggesting seizures as predictive for a poor prognosis.ConclusionsConsidering early, but less specific neuropsychiatric signs may accelerate the path to diagnosing NP-C in a patient.

Plasma Lysosphingomyelin Demonstrates Great Potential as a Diagnostic Biomarker for Niemann-Pick Disease Type C in a Retrospective Study

Niemann-Pick disease type C (NP-C) is a devastating, neurovisceral lysosomal storage disorder which is characterised by variable manifestation of visceral signs, progressive neuropsychiatric deterioration and premature death, caused by mutations in the NPC1 and NPC2 genes. Due to the complexity of diagnosis and the availability of an approved therapy in the EU, improved detection of NP-C may have a huge impact on future disease management. At the cellular level dysfunction or deficiency of either the NPC1 or NPC2 protein leads to a complex intracellular endosomal/lysosomal trafficking defect, and organ specific patterns of sphingolipid accumulation. Lysosphingolipids have been shown to be excellent biomarkers of sphingolipidosis in several enzyme deficient lysosomal storage disorders. Additionally, in a recent study the lysosphingolipids, lysosphingomyelin (SPC) and glucosylsphingosine (GlcSph), appeared to be elevated in the plasma of three adult NP-C patients. In order to investigate the clinical utility of SPC and GlcSph as diagnostic markers, an in-depth fit for purpose biomarker assay validation for measurement of these biomarkers in plasma by liquid chromatography-tandem mass spectrometry was performed. Plasma SPC and GlcSph are stable and can be measured accurately, precisely and reproducibly. In a retrospective analysis of 57 NP-C patients and 70 control subjects, median plasma SPC and GlcSph were significantly elevated in NP-C by 2.8-fold and 1.4-fold respectively. For miglustat-naïve NP-C patients, aged 2–50 years, the area under the ROC curve was 0.999 for SPC and 0.776 for GlcSph. Plasma GlcSph did not correlate with SPC levels in NP-C patients. The data indicate excellent potential for the use of lysosphingomyelin in NP-C diagnosis, where it could be used to identify NP-C patients for confirmatory genetic testing.

Relative acidic compartment volume as a lysosomal storage disorder–associated biomarker

Lysosomal storage disorders (LSDs) occur at a frequency of 1 in every 5,000 live births and are a common cause of pediatric neurodegenerative disease. The relatively small number of patients with LSDs and lack of validated biomarkers are substantial challenges for clinical trial design. Here, we evaluated the use of a commercially available fluorescent probe, Lysotracker, that can be used to measure the relative acidic compartment volume of circulating B cells as a potentially universal biomarker for LSDs. We validated this metric in a mouse model of the LSD Niemann-Pick type C1 disease (NPC1) and in a prospective 5-year international study of NPC patients. Pediatric NPC subjects had elevated acidic compartment volume that correlated with age-adjusted clinical severity and was reduced in response to therapy with miglustat, a European Medicines Agency–approved drug that has been shown to reduce NPC1-associated neuropathology. Measurement of relative acidic compartment volume was also useful for monitoring therapeutic responses of an NPC2 patient after bone marrow transplantation. Furthermore, this metric identified a potential adverse event in NPC1 patients receiving i.v. cyclodextrin therapy. Our data indicate that relative acidic compartment volume may be a useful biomarker to aid diagnosis, clinical monitoring, and evaluation of therapeutic responses in patients with lysosomal disorders.

Acetyl-dl-leucine in Niemann-Pick type C A case series

Objective: To assess the effects of the modified amino acid acetyl-dl-leucine (AL) on cerebellar ataxia, eye movements, and quality of life of patients with Niemann-Pick type C (NP-C) disease. Methods: Twelve patients with NP-C disease were treated with AL 3 g/d for 1 week and then with 5 g/d for 3 weeks with a subsequent washout period of 1 month. The Scale for the Assessment and Rating of Ataxia (SARA), the Spinocerebellar Ataxia Functional Index (SCAFI), the modified Disability Rating Scale (mDRS), EuroQol 5Q-5D-5L, and the visual analog scale (VAS) were administered. Measurements took place at baseline, after 1 month of therapy, and after 1 month of washout. Results: The SARA score changed from the baseline (median [±SD, interquartile range]) of 10.8 (11.2, 8–24.6) to 7.0 (10.7, 5.6–19.6) on medication (difference: 3.8 points) and 10.5 (11.5, 7.1–23.9) after washout (difference: 3.5 points) (p = 0.000412; post hoc p = 0.003 between baseline and on medication, and on medication and washout p = 0.005). The SCAFI subscore 9-Hole Peg Test for dominant hand, mDRS score, and VAS score also improved on medication. No side effects except transient dizziness in one patient were reported. Conclusions: Treatment with AL improved ataxic symptoms in patients with NP-C without relevant side effects, thus showing a reasonable risk-benefit profile. Classification of evidence: This study provides Class IV evidence that AL improves cerebellar symptoms and quality of life in patients with NP-C.

Clinical and Neuroradiological Aspects of the Different Types

The different types (I–VII) of mucopolysaccharidoses (MPS), a hereditary lysosomal storage disorder where the enzyme defect leads to glycosaminoglycan deposits in different tissues, present with characteristic lesions of the central nervous system (CNS). This review reports the CT and MRI findings of patients suffering from mucopolysaccharidosis in the context with aspects of biochemistry, pathophysiology, histological findings and clinical course. Neuroradiological findings include hydrocephalus, focal or global brain atrophy, and spinal cord compression at the atlantoaxial joint. Cribriform white matter lesions, corresponding to mucopolysaccharide deposition in the enlarged perivascular space, combined with leukencephalopathy are found in about half of the patients. Another half of the patients show minor to severe myelopathy at the atlantoaxial joint due to cervical cord compression. These findings are observed mainly in patients with MPS type IV, but as well in nearly all patients with MPS type VI. In the literature brain involvement is described exclusively in MPS type I, II and III, but the authors show definite demyelination and widening of the perivascular space in a number of patients with MPS type VI, who additionally suffered from progressive visual deficits, caused by ocular and/or optic nerve involvement.ZusammenfassungDie verschiedenen Formen der Mukopolysaccharidosen (MPS), einer hereditären, lysosomalen Speicherkrankheit, die, bedingt durch einen Enzymdefekt, zu Glykosaminoglykanablagerungen in verschiedenen Geweben führt, weisen charakteristische Veränderungen des zentralen Nervensystems (ZNS) aus. In dieser Übersichtsarbeit werden die CT- und MRT-Befunde von Patienten mit Mukopolysaccharidosen in Zusammenhang mit biochemischen, pathophysiologischen und pathohistologischen Befunden sowie charakteristischen klinischen Symptomen und im Verlauf vorgestellt. Die neuroradiologischen Befunde des ZNS weisen neben einem Hydrozephalus, einer fokalen und/oder globalen Atrophie auch eine medulläre Kompression am kraniozervikalen Übergang auf. Hinzu kommen erweiterte perivaskuläre Räume und Veränderungen der weißen Substanz. In jeweils etwa der Hälfte aller Patienten werden diese sog. cribriformen Läsionen (bedingt durch perivaskuläre Mukopolysaccharidablagerungen) und eine Leukenzephalopathie sowie eine hohe zervikale Myelonkompression mit unterschiedlich ausgeprägter Myelomalazie gefunden. Diese Befunde sind in erster Linie bei Patienten mit MPS IV, aber auch in der Mehrzahl der Patienten mit MPS VI zu finden. In der Literatur wird angegeben, dass eine ZNS-Beteiligung lediglich bei Patienten mit MPS I, II und III zu finden ist, die Autoren haben jedoch Demyelinisierung und erweiterte perivaskuläre Räume auch bei Patienten mit MPS VI nachgewiesen, die zusätzlich auch an progredienter Visusminderung litten, bedingt durch eine Beteiligung der Kornea und/oder des Nervus opticus.

Alpha-mannosidosis: correlation between phenotype, genotype and mutant MAN2B1 subcellular localisation

BackgroundAlpha-mannosidosis is caused by mutations in MAN2B1, leading to loss of lysosomal alpha-mannosidase activity. Symptoms include intellectual disabilities, hearing impairment, motor function disturbances, facial coarsening and musculoskeletal abnormalities.MethodsTo study the genotype-phenotype relationship for alpha-mannosidosis 66 patients were included. Based on the predicted effect of the mutations and the subcellular localisation of mutant MAN2B1 in cultured cells, the patients were divided into three subgroups.Clinical and biochemical data were collected. Correlation analyses between each of the three subgroups of genotype/subcellular localisation and the clinical and biochemical data were done to investigate the potential relationship between genotype and phenotype in alpha-mannosidosis.Statistical analyses were performed using the SPSS software. Analyses of covariance were performed to describe the genotype-phenotype correlations. The phenotype parameters were modelled by the mutation group and age as a covariate. P values of <0.05 were considered as statistically significant.ResultsComplete MAN2B1 genotypes were established for all patients. We found significantly higher scores in the Leiter-R test, lower concentrations of CSF-oligosaccharides, higher point scores in the Bruininks-Oseretsky Test of Motor Proficiency subtests (BOT-2); Upper limb coordination and Balance, and a higher FVC% in patients in subgroup 3, harbouring at least one variant that allows localisation of the mutant MAN2B1 protein to the lysosomes compared to subgrou 2 and/or subgroup 1 with no lysosomal localization of the mutant MAN2B1 protein.ConclusionOur results indicate a correlation between the MAN2B1 genotypes and the cognitive function, upper limb coordination, balance, FVC% and the storage of oligosaccharides in CSF. This correlation depends on the subcellular localisation of the mutant MAN2B1 protein.

Retinal and optic nerve degeneration in α-mannosidosis

Backgroundα-mannosidosis is a rare, autosomal-recessive, lysosomal storage disease caused by a deficient activity of α-mannosidase. Typical symptoms include intellectual, motor and hearing impairment, facial coarsening, and musculoskeletal abnormalities. Ocular pathologies reported previously were mainly opacities of the cornea and lens, strabismus, and ocular motility disorders. However, retinal and optic nerve degeneration have been rarely described.MethodsWe report ocular findings of 32 patients with α-mannosidosis. We particularly concentrated on retinal abnormalities which we supported by posterior segment examination, fundus photography, and Spectral-Domain optical coherence tomography (SD-OCT) imaging.ResultsTapeto-retinal degeneration with bone spicule formations in the peripheral retina or macular changes were seen in three patients (9.4%) on funduscopy; of these, two with optic nerve atrophy. Eight retinal images could be obtained by OCT or fundus photography; of these, six showed thinning of the outer retinal layers on OCT. Overall, optic nerve atrophy was seen in six patients (18.8%); of these, four with partial atrophy. Two patients had partial optic nerve atrophy with no retinal abnormalities on funduscopy. Cataract was seen in two (6.3%), corneal haze also in two patients (6.3%). Six patients (18.8%) had manifest strabismus, four (12.5%) nystagmus, and in five patients (15.6%) impaired smooth pursuit eye movements were seen.ConclusionOcular pathologies are not exclusively confined to opacities of the cornea and lens or strabismus and ocular motility disorders but tapeto-retinal degeneration and optic nerve atrophy may be a common feature in α-mannosidosis. OCT technology helps detecting early outer retinal thinning which can progress with age and potentially leads to vision loss over time.

Health Related Quality of Life, Disability, and Pain in Alpha Mannosidosis: Long-Term Data of Enzyme Replacement Therapy With Velmanase Alfa (Human Recombinant Alpha Mannosidase)

Alpha-mannosidosis, a rare lysosomal storage disorder caused by deficiency of the lysosomal enzyme alpha-mannosidase, results in accumulation of mannose-rich glycoproteins in the tissues and sequel...