A Suspicion Index to aid screening of early-onset Niemann-Pick disease Type C (NP-C)

Challenges in the Definitive Diagnosis of Niemann-Pick Type C-Leaky Variants and Alternative Transcripts

Niemann-Pick type C (NPC, ORPHA: 646) is a neuro-visceral, psychiatric disease caused predominantly by pathogenic variants in the NPC1 gene or seldom in NPC2. The rarity of the disease, and its wide range of clinical phenotypes and ages of onset, turn the diagnosis into a significant challenge. Other than the detailed clinical history, the typical diagnostic work-up for NPC includes the quantification of pathognomonic metabolites. However, the molecular basis diagnosis is still of utmost importance to fully characterize the disorder. Here, the authors provide an overview of splicing variants in the NPC1 and NPC2 genes and propose a new workflow for NPC diagnosis. Splicing variants cover a significant part of the disease-causing variants in NPC. The authors used cDNA analysis to study the impact of such variants, including the collection of data to classify them as leaky or non-leaky pathogenic variants. However, the presence of naturally occurring spliced transcripts can misdiagnose or mask a pathogenic variant and make the analysis even more difficult. Analysis of the NPC1 cDNA in NPC patients in parallel with controls is vital to assess and detect alternatively spliced forms. Moreover, nonsense-mediated mRNA decay (NMD) analysis plays an essential role in evaluating the naturally occurring transcripts during cDNA analysis and distinguishing them from other pathogenic variants' associated transcripts.

MicroRNA Profile, Putative Diagnostic Biomarkers and RNA-Based Therapies in the Inherited Lipid Storage Disease Niemann-Pick Type C

Lipids are essential for cellular function and are tightly controlled at the transcriptional and post-transcriptional levels. Dysregulation of these pathways is associated with vascular diseases, diabetes, cancer, and several inherited metabolic disorders. MicroRNAs (miRNAs), in particular, are a family of post-transcriptional gene repressors associated with the regulation of many genes that encode proteins involved in multiple lipid metabolism pathways, thereby influencing their homeostasis. Thus, this class of non-coding RNAs (ncRNAs) has emerged as a promising therapeutic target for the treatment of lipid-related metabolic alterations. Most of these miRNAs act at an intracellular level, but in the past few years, a role for miRNAs as intercellular signaling molecules has also been uncovered since they can be transported in bodily fluids and used as potential biomarkers of lipid metabolic alterations. In this review, we point out the current knowledge on the miRNA signature in a lysosomal storage disorder associated with lipid dysfunction, Niemann-Pick type C, and discuss the potential use of miRNAs as biomarkers and therapeutic targets for RNA-based therapies.

The Niemann-Pick type diseases – A synopsis of inborn errors in sphingolipid and cholesterol metabolism

Disturbances of lipid homeostasis in cells provoke human diseases. The elucidation of the underlying mechanisms and the development of efficient therapies represent formidable challenges for biomedical research. Exemplary cases are two rare, autosomal recessive, and ultimately fatal lysosomal diseases historically named "Niemann-Pick" honoring the physicians, whose pioneering observations led to their discovery. Acid sphingomyelinase deficiency (ASMD) and Niemann-Pick type C disease (NPCD) are caused by specific variants of the sphingomyelin phosphodiesterase 1 (SMPD1) and NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2) genes that perturb homeostasis of two key membrane components, sphingomyelin and cholesterol, respectively. Patients with severe forms of these diseases present visceral and neurologic symptoms and succumb to premature death. This synopsis traces the tortuous discovery of the Niemann-Pick diseases, highlights important advances with respect to genetic culprits and cellular mechanisms, and exposes efforts to improve diagnosis and to explore new therapeutic approaches.

Estimating the prevalence of Niemann-Pick disease type C (NPC) in the United States

BACKGROUND

Niemann-Pick Disease Type C (NPC) is an ultra-rare progressive neurodegenerative disease caused by autosomal recessive mutations in the NPC1 or NPC2 genes that lead to premature death, with most individuals dying between 10 and 25 years of age. NPC can present at any age and many individuals with NPC may be misdiagnosed or undiagnosed. A key challenge with recognizing NPC is the heterogeneous and nonspecific clinical presentation. Currently, there are no approved treatments for NPC in the United States; miglustat, an FDA-approved treatment for Gaucher disease, is used off-label for NPC and GM1 gangliosidosis.

OBJECTIVES

To estimate the number of people in the United States that 1) have an NPC diagnosis 2) have an NPC diagnosis and/or are treated off-label with miglustat for NPC and 3) are likely to have NPC.

METHODS

For the first two objectives, patients were identified using the Symphony Integrated DataVerse database (Oct 2015-Jan 2020). To identify the number of people with NPC for Objective 1, cases of NPC were defined as any patients with an ICD-10 code of E75.242 (NPC) during the study period. Objective 2 expands upon Objective 1, including (a) patients from Objective 1 and (b) patients with documented miglustat use (NDC 43975-0310 or 10,148-0201) who did not have any claim with Gaucher disease (ICD-10 E75.22) or GM1 gangliosidosis (ICD-10 E75.1) during the study period. For the third objective, published NPC incidence (1 per 89,000 live births) and expected mortality estimates were applied to the 2018 United States birth rate (11.6 per 1000) and population size (326.7 million).

RESULTS

A total of 308 million unique individuals were represented in the database. Of these, 294 individuals had an NPC diagnosis, yielding an identified NPC prevalence of 0.95 per million people in the United States. 305 individuals were diagnosed with NPC and/or were treated with miglustat without having a diagnosis for either Gaucher or GM1 gangliosidosis, yielding an NPC diagnosed or treated prevalence of 0.99 per million people in the United States. Based on the published literature, there are an estimated 42 new NPC cases per year. Applying this number to the distribution of NPC type (based on age of neurologic symptom onset) and corresponding mortality estimates generates an estimated 943 prevalent cases of NPC, or 2.9 cases of NPC per million people in the United States.

CONCLUSIONS

NPC is an ultra-rare, progressive neurodegenerative disease with approximately 1 per million people in the United States diagnosed with or treated off-label for NPC. Given that NPC is often misdiagnosed or undiagnosed, the estimated prevalence from the epidemiology calculations (2.9 per million) approximates the number of NPC cases if disease awareness, screening and diagnosis efforts were enhanced.

Neurodevelopmental Characterization of Young Children Diagnosed with Niemann-Pick Disease, Type C1

OBJECTIVE

Niemann-Pick disease type C1 (NPC1) is a lysosomal storage disease characterized by progressive neurodegeneration, with the age of diagnosis ranging from the prenatal period through adulthood. Although neurological symptoms usually precede genetic diagnosis, they do not necessarily prompt diagnosis in the early years. Few prospective data are available to describe neurological onset, including neurodevelopmental delays, in children with NPC1. This dearth of information hinders the planning and implementation of adequate monitoring and treatment for the neurodevelopmental sequelae of NPC1.

METHOD

Twenty-nine infants, toddlers, and preschoolers younger than 6 years participated in a natural history study and were administered neurodevelopmental assessments using instruments commonly used for early intervention screening in the community.

RESULTS

Twenty-two of 29 participants met the criteria for a significant delay of at least 1.5 SDs below the mean in at least one domain of development; the youngest children often met these criteria for a significant delay based on motor delays, but cognitive and language delays were also common. However, only 11 of the 22 participants were reported to receive early intervention services before study entry.

CONCLUSION

Although neurological symptoms may not prompt the genetic diagnosis of NPC1, the current findings support the use of a multimethod approach to repeated assessments for young children with the diagnosis because of the frequency of developmental delays or decline in multiple domains. The diagnosis of NPC1 alone should qualify children for evaluation for early intervention services and consideration of investigational therapeutic interventions.

Inherited disorders of lysosomal membrane transporters

Disorders caused by defects in lysosomal membrane transporters form a distinct subgroup of lysosomal storage disorders (LSDs). To date, defects in only 10 lysosomal membrane transporters have been associated with inherited disorders. The clinical presentations of these diseases resemble the phenotypes of other LSDs; they are heterogeneous and often present in children with neurodegenerative manifestations. However, for pathomechanistic and therapeutic studies, lysosomal membrane transport defects should be distinguished from LSDs caused by defective hydrolytic enzymes. The involved proteins differ in function, localization, and lysosomal targeting, and the diseases themselves differ in their stored material and therapeutic approaches. We provide an overview of the small group of disorders of lysosomal membrane transporters, emphasizing discovery, pathomechanism, clinical features, diagnostic methods and therapeutic aspects. We discuss common aspects of lysosomal membrane transporter defects that can provide the basis for preclinical research into these disorders.

Clinical and Molecular Features of Early Infantile Niemann Pick Type C Disease

Niemann Pick disease type C (NPC) is a neurovisceral disorder due to mutations in NPC1 or NPC2. This review focuses on poorly characterized clinical and molecular features of early infantile form of NPC (EIF) and identified 89 cases caused by NPC1 (NPC1) and 16 by NPC2 (NPC2) mutations. Extra-neuronal features were common; visceromegaly reported in 80/89 NPC1 and in 15/16 NPC2, prolonged jaundice in 30/89 NPC1 and 7/16 NPC2. Early lung involvement was present in 12/16 NPC2 cases. Median age of neurological onset was 12 (0-24) and 7.5 (0-24) months in NPC1 and NPC2 groups, respectively. Developmental delay and hypotonia were the commonest first detected neurological symptoms reported in 39/89 and 18/89 NPC1, and in 8/16 and 10/16 NPC2, respectively. Additional neurological symptoms included vertical supranuclear gaze palsy, dysarthria, cataplexy, dysphagia, seizures, dystonia, and spasticity. The following mutations in homozygous state conferred EIF: deletion of exon 1+promoter, c.3578_3591 + 9del, c.385delT, p.C63fsX75, IVS21-2delATGC, c. 2740T>A (p.C914S), c.3584G>T (p.G1195V), c.3478-6T>A, c.960_961dup (p.A321Gfs*16) in NPC1 and c.434T>A (p.V145E), c.199T>C (p.S67P), c.133C>T (p.Q45X), c.141C>A (p.C47X) in NPC2. This comprehensive analysis of the EIF type of NPC will benefit clinical patient management, genetic counselling, and assist design of novel therapy trials.

Diagnosis support systems for rare diseases: a scoping review

INTRODUCTION

Rare diseases affect approximately 350 million people worldwide. Delayed diagnosis is frequent due to lack of knowledge of most clinicians and a small number of expert centers. Consequently, computerized diagnosis support systems have been developed to address these issues, with many relying on rare disease expertise and taking advantage of the increasing volume of generated and accessible health-related data. Our objective is to perform a review of all initiatives aiming to support the diagnosis of rare diseases.

METHODS

A scoping review was conducted based on methods proposed by Arksey and O'Malley. A charting form for relevant study analysis was developed and used to categorize data.

RESULTS

Sixty-eight studies were retained at the end of the charting process. Diagnosis targets varied from 1 rare disease to all rare diseases. Material used for diagnosis support consisted mostly of phenotype concepts, images or fluids. Fifty-seven percent of the studies used expert knowledge. Two-thirds of the studies relied on machine learning algorithms, and one-third used simple similarities. Manual algorithms were encountered as well. Most of the studies presented satisfying performance of evaluation by comparison with references or with external validation. Fourteen studies provided online tools, most of which aimed to support the diagnosis of all rare diseases by considering queries based on phenotype concepts.

CONCLUSION

Numerous solutions relying on different materials and use of various methodologies are emerging with satisfying preliminary results. However, the variability of approaches and evaluation processes complicates the comparison of results. Efforts should be made to adequately validate these tools and guarantee reproducibility and explicability.

Recessive Ataxia Differential Diagnosis Algorithm (RADIAL) Versus Specific Niemann-Pick Type C Suspicion Indices: A Retrospective Algorithm Comparison

Early diagnosis of Niemann-Pick disease type C (NPC) is crucial to slow the progression of neurological manifestations. Different tools were developed to aid diagnosis of NPC, but to date, no study has compared their performance. We aimed to compare the RADIAL algorithm, intended for the differential diagnosis of autosomal recessive cerebellar ataxias (ARCAs) and NPC-specific suspicion indices (SIs). This study was a retrospective analysis of data from 834 patients with molecularly confirmed ARCAs, including 57 NPC cases (RADIAL cohort). We aimed to compare the algorithm performance of RADIAL (Top 1 and Top 3) with that of four SIs (Original, Refined, 2/3 and 2/7) in discriminating NPC cases and non-NPC cases. We also identified ARCAs closely related to NPC as those with low specificity to detect non-NPC cases and described differential and overlapping features with NPC. Overall, excellent sensitivity and specificity (> 0.90) were achieved with both RADIAL and SI tools for NPC cases. The highest sensitivity was attained with the 2/7 SI, Refined SI and Top 3 RADIAL algorithms. Top 1 and Top 3 RADIAL were the most specific tools, followed by the Original SI. The individual comparison of each ARCA revealed that Wilson disease, PLA2G6-associated neurodegeneration, and hypomyelinating leukodystrophy (POLR3A) are frequent NPC false positives (PLA2G6 and POL3A only with the SIs). Both RADIAL and SI diagnostic approaches showed strong discriminatory potential and may be useful screening tools in different clinical contexts.

Evaluation of different suspicion indices in identifying patients with Niemann-Pick disease Type C in clinical practice: a post hoc analysis of a retrospective chart review

BACKGROUND

Niemann-Pick disease Type C (NP-C) is a lysosomal lipid storage disorder with varying symptomatology depending on the age of onset. The diagnosis of NP-C is challenging due to heterogeneous nonspecific clinical presentation of the disease. NP-C Suspicion Index (SI) was developed to aid screening and identification of patients with suspicion of NP-C for further clinical evaluation. Here we assess the performance of five NP-C SI models to identify patients with NP-C compared with clinical practice to determine the best SI model for identification of each clinical form of NP-C by age.

METHODS

This was a post hoc analysis of a retrospective chart review of patient data collected from five expert NP-C centers. The study assessed the proportion of patients with NP-C who could have been identified using the Original SI, Refined SI, 2/7 SI, 2/3 SI, and Early-Onset SI and evaluated the performance of each SI against clinical practice. A score above a threshold of 70 points for the Original SI, 40 points for the Refined SI, 6 points for the Early-Onset SI, and 2 points for the 2/7 and 2/3 SIs represented identification of NP-C.

RESULTS

The study included 63 patients, and of these, 23.8% had a family history of NP-C. Of the available SI tools, the Refined SI performed well in identifying patients with NP-C across all age groups (77.8% infantile, 100% juvenile and 100% adult groups), and earlier identification than clinical diagnosis would have been possible in 50.0% of infantile, 72.7% of juvenile and 87.0% of adult patients. Patients who were not detected by the Refined SI prior to clinical diagnosis mainly presented with delayed developmental milestones, visceral manifestations, neurologic hypotonia, clumsiness, ataxia, vertical supranuclear gaze palsy, parent or siblings with NP-C, dysarthria/dysphagia and psychotic symptoms.

CONCLUSION

This study demonstrated the applicability of various SI models for screening and identification of patients with NP-C for further clinical evaluation. Although NP-C is rare and the patient population is limited, this study was conducted in a real-world setting and confirms SI models as useful screening tools that facilitate identification of patients with NP-C earlier in their disease course.

Disease characteristics, prognosis and miglustat treatment effects on disease progression in patients with Niemann-Pick disease Type C: an international, multicenter, retrospective chart review

BACKGROUND

Niemann-Pick disease Type C (NP-C) is a lysosomal lipid storage disorder characterized by progressive neurodegenerative symptomatology. The signs and symptoms of NP-C vary with age at disease onset, and available therapies are directed at alleviating symptoms and stabilizing disease progression. We report the characteristics and factors related to disease progression, and analyze the effect of miglustat treatment on disease progression and patient survival using NP-C disability scales.

METHODS

This retrospective, observational chart review included patients with NP-C from five expert NP-C centers. Patient disability scores were recorded using three published NP-C disability scales, and a unified disability scale was developed to allow comparison of data from each scale. Disease progression was represented by scores on the unified NP-C disability scale. Patients were stratified as infantile (< 4 years), juvenile (≥ 4 - < 16 years), and adult (≥ 16 years) based on age at diagnosis, and treated ≥1 year and non-treated/treated < 1 year based on the duration of miglustat treatment.

RESULTS

The analysis included 63 patients; the majority (61.9%) were on miglustat therapy for ≥1 year. Ataxia and clumsiness/frequent fall were the most common neurologic symptoms across age groups, whereas, hypotonia and delayed developmental milestones were specific to infantile patients. In both infantile and juvenile patients, visceral signs preceded diagnosis and neurologic signs were noted at or shortly after diagnosis. Adult patients presented with a range of visceral, neurologic, and psychiatric signs in years preceding diagnosis. Patients on miglustat therapy for ≥1 year had a lower mean annual disease progression compared with those untreated/treated < 1 year (1.32 vs 3.54 points/year). A significant reduction in annual disease progression in infantile patients, and a trend towards reduced disease progression in juvenile patients after ≥1 year of miglustat treatment, translated into higher age at last contact or death in these groups.

CONCLUSIONS

The type and onset of symptoms varied across age groups and were consistent with descriptions of NP-C within the literature. Miglustat treatment was associated with a reduced rate of disability score worsening in infantile and juvenile patients, both in agreement with increased age at last contact.

Psychiatric and neurological symptoms in patients with Niemann-Pick disease type C (NP-C): Findings from the International NPC Registry

Objectives: Niemann-Pick disease type C (NP-C) is a rare inherited neurovisceral disease that should be recognised by psychiatrists as a possible underlying cause of psychiatric abnormalities. This study describes NP-C patients who had psychiatric manifestations at enrolment in the international NPC Registry, a unique multicentre, prospective, observational disease registry. Methods: Treating physicians' data entries describing psychiatric manifestations in NPC patients were coded and grouped by expert psychiatrists. Results: Out of 386 NP-C patients included in the registry as of October 2015, psychiatric abnormalities were reported to be present in 34% (94/280) of those with available data. Forty-four patients were confirmed to have identifiable psychiatric manifestations, with text describing these psychiatric manifestations. In these 44 patients, the median (range) age at onset of psychiatric manifestations was 17.9 years (2.5-67.9; n = 15), while the median (range) age at NP-C diagnosis was 23.7 years (0.2-69.8; n = 34). Almost all patients (43/44; 98%) had an occurrence of ≥1 neurological manifestation at enrolment. Conclusions: These data show that substantial delays in diagnosis of NP-C are long among patients with psychiatric symptoms and, moreover, patients presenting with psychiatric features and at least one of cognitive impairment, neurological manifestations, and/or visceral symptoms should be screened for NP-C.

Thinking outside the box: cataplexy without narcolepsy

Cataplexy is a transient loss of muscle tone that can be triggered by emotions such as laughter, excitement or fear. Other causes of cataplexy include Niemann-Pick type C Disease, Angelman Syndrome, Norrie Disease, Prader-Willi Syndrome. In addition, cataplexy can be a side effect of several drugs (eg, lamotrigine, clozapine, and gamma-hydroxybutyrate). Yet, the most prevalent causes of cataplexy without narcolepsy are rare genetic diseases; which explains why cataplexy is classically linked to narcolepsy. Therefore, it is essential disconnecting cataplexy from narcolepsy especially in pediatric population and after use of a few medications. In this review, we described few conditions of cataplexy not related to narcolepsy. We performed a review of literature (MEDLINE and EMBASE database), without limited date or publication restrictions.

Recommendations for patient screening in ultra-rare inherited metabolic diseases: what have we learned from Niemann-Pick disease type C?

BACKGROUND

Rare and ultra-rare diseases (URDs) are often chronic and life-threatening conditions that have a profound impact on sufferers and their families, but many are notoriously difficult to detect. Niemann-Pick disease type C (NP-C) serves to illustrate the challenges, benefits and pitfalls associated with screening for ultra-rare inborn errors of metabolism (IEMs). A comprehensive, non-systematic review of published information from NP-C screening studies was conducted, focusing on diagnostic methods and study designs that have been employed to date. As a key part of this analysis, data from both successful studies (where cases were positively identified) and unsuccessful studies (where the chosen approach failed to identify any cases) were included alongside information from our own experiences gained from the planning and execution of screening for NP-C. On this basis, best-practice recommendations for ultra-rare IEM screening are provided. Twenty-six published screening studies were identified and categorised according to study design into four groups: 1) prospective patient cohort and family-based secondary screenings (18 studies); 2) analyses of archived 'biobank' materials (one study); 3) medical chart review and bioinformatics data mining (five studies); and 4) newborn screening (two studies). NPC1/NPC2 sequencing was the most common primary screening method (Sanger sequencing in eight studies and next-generation sequencing [gene panel or exome sequencing] in five studies), followed by biomarker analyses (usually oxysterols) and clinical surveillance.

CONCLUSIONS

Historically, screening for NP-C has been based on single-patient studies, small case series, and targeted cohorts, but the emergence of new diagnostic methods over the last 5-10 years has provided opportunities to screen for NP-C on a larger scale. Combining clinical, biomarker and genetic diagnostic methods represents the most effective way to identify NP-C cases, while reducing the likelihood of misdiagnosis. Our recommendations are intended as a guide for planning screening protocols for ultra-rare IEMs in general.

Miglustat in Niemann-Pick disease type C patients: a review

OBJECTIVE

Niemann-Pick disease type C (NP-C) is a rare, autosomal recessive, neurodegenerative disease associated with a wide variety of progressive neurological manifestations. Miglustat is indicated for the treatment of progressive neurological manifestations in both adults and children. Since approval in 2009 there has been a vast growth in clinical experience with miglustat. The effectiveness of miglustat has been assessed using a range of measures.

METHODS

Comprehensive review of published data from studies of cellular neuropathological markers and structural neurological indices in the brain, clinical impairment/disability, specific clinical neurological manifestations, and patient survival.

RESULTS

Cranial diffusion tensor imaging and magnetic resonance spectroscopy studies have shown reduced levels of choline (a neurodegeneration marker), and choline/N-acetyl aspartate ratio (indicating increased neuronal viability) in the brain during up to 5 years of miglustat therapy, as well as a slowing of reductions in fractional anisotropy (an axonal/myelin integrity marker). A 2-year immunoassay study showed significant reductions in CSF-calbindin during treatment, indicating reduced cerebellar Purkinje cell loss. Magnetic resonance imaging studies have demonstrated a protective effect of miglustat on cerebellar and subcortical structure that correlated with clinical symptom severity. Numerous cohort studies assessing core neurological manifestations (impaired ambulation, manipulation, speech, swallowing, other) using NP-C disability scales indicate neurological stabilization over 2-8 years, with a trend for greater benefits in patients with older (non-infantile) age at neurological onset. A randomized controlled trial and several cohort studies have reported improvements or stabilization of saccadic eye movements during 1-5 years of therapy. Swallowing was also shown to improve/remain stable during the randomized trial (up to 2 years), as well as in long-term observational cohorts (up to 6 years). A meta-analysis of dysphagia - a potent risk factor for aspiration pneumonia and premature death in NP-C - demonstrated a survival benefit with miglustat due to improved/stabilized swallowing function.

CONCLUSIONS

The effects of miglustat on neurological NP-C manifestations has been assessed using a range of approaches, with benefits ranging from cellular changes in the brain through to visible clinical improvements and improved survival.

[Niemann-Pick type C disease in a child]

The authors consider a clinical case of Niemann-Pick disease type C, an orphan hereditary autosomal recessive neurodegenerative disease belonging to the group of lysosomal storage disease, in an 11-year female patient with the late infantile form of the disease. The combination of psychomotor retardation, polymorphic neurological symptoms and physical changes in the form of isolated splenomegaly suggested the diagnosis of Niemann-Pick type C disease. DNA testing was carried out using direct automated sequencing. The patient was treated with miglustat.

Niemann-Pick disease type C in the newborn period: a single-center experience

Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal storage disorder with a great variation in clinical spectrum and age at presentation. Clinical features of 10 NPC patients who presented in the newborn period between 1993 and 2015 at our center were retrospectively analyzed. Males and females were equally distributed; there was a history of parental consanguinity (n = 8) and first-degree relative with NPC (n = 3). Patients were symptomatic between 1 and 10 days (mean 3.6 ± 2.6 days). Age at diagnosis was between 1 and 30 days (mean 14.6 ± 13.3 days). Laboratory work-up included bone marrow aspiration (n = 8) and/or filipin staining (n = 4). Confirmation was done by molecular analysis, indicating NPC1 (n = 8) and NPC2 (n = 2) mutations. All patients had neonatal cholestasis and hepatosplenomegaly. Pulmonary involvement (n = 9) and fetal ascites (n = 2) were additional accompanying features. All but one died due to pulmonary complications (n = 6) and liver insufficiency (n = 3) between 1.5 and 36 months of age (mean 8.1 ± 10.8 months). Currently, one patient is alive at the age of 11 months without any neurological deficit.

CONCLUSIONS

Neonatal presentation is a rare form of NPC with exclusively visceral involvement in the newborn period and poor prognosis leading to premature death due to pulmonary complications and liver failure. What is known: • Neonatal presentation is a rare form of NPC with exclusively visceral involvement in the newborn period and poor prognosis leading to premature death. • Progressive liver disease is the most common cause of death among neonatal-onset NPC patients. What is new: • Natural course of neonatal-onset NPC may show variations. • Pulmonary involvement should be considered as an important cause of death in neonatal-onset cases, and appropriate precautions should be taken to prevent complications of respiratory insufficiency and airway infections.

Recommendations for the detection and diagnosis of Niemann-Pick disease type C: An update

Purpose of review:

Niemann-Pick disease type C (NP-C) is a neurovisceral disorder that may be more prevalent than earlier estimates. Diagnosis of NP-C is often delayed; a key aim for clinical practice is to reduce this delay. Recently, substantial progress has been made in the field of NP-C screening and diagnosis, justifying an update to the existing recommendations for clinical practice.

Recent findings:

New biomarker profiling and genetic analysis technologies are included as first-line diagnostic tests for NP-C. Most diagnoses can now be confirmed by combination of biomarker and genetic analyses. Filipin staining may facilitate diagnosis in uncertain cases. Recommendations are provided for psychiatrists, neuro-ophthalmologists, and radiologists, and on screening within specific at-risk patient cohorts. The NP-C diagnostic algorithm has been updated and simplified.

Summary:

This publication provides expert recommendations for clinicians who may see patients presenting with the signs and symptoms of NP-C, including general practitioners, pediatricians, neurologists, and psychiatrists.

The hidden Niemann-Pick type C patient: clinical niches for a rare inherited metabolic disease

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare, inherited neurodegenerative disease of impaired intracellular lipid trafficking. Clinical symptoms are highly heterogeneous, including neurological, visceral, or psychiatric manifestations. The incidence of NP-C is under-estimated due to under-recognition or misdiagnosis across a wide range of medical fields. New screening and diagnostic methods provide an opportunity to improve detection of unrecognized cases in clinical sub-populations associated with a higher risk of NP-C. Patients in these at-risk groups ("clinical niches") have symptoms that are potentially related to NP-C, but go unrecognized due to other, more prevalent clinical features, and lack of awareness regarding underlying metabolic causes.

METHODS

Twelve potential clinical niches identified by clinical experts were evaluated based on a comprehensive, non-systematic review of literature published to date. Relevant publications were identified by targeted literature searches of EMBASE and PubMed using key search terms specific to each niche. Articles published in English or other European languages up to 2016 were included.

FINDINGS

Several niches were found to be relevant based on available data: movement disorders (early-onset ataxia and dystonia), organic psychosis, early-onset cholestasis/(hepato)splenomegaly, cases with relevant antenatal findings or fetal abnormalities, and patients affected by family history, consanguinity, and endogamy. Potentially relevant niches requiring further supportive data included: early-onset cognitive decline, frontotemporal dementia, parkinsonism, and chronic inflammatory CNS disease. There was relatively weak evidence to suggest amyotrophic lateral sclerosis or progressive supranuclear gaze palsy as potential niches.

CONCLUSIONS

Several clinical niches have been identified that harbor patients at increased risk of NP-C.

Differences in Niemann-Pick disease Type C symptomatology observed in patients of different ages

BACKGROUND

Niemann-Pick disease Type C (NP-C) is a genetic lipid storage disorder characterised by progressive neurovisceral symptomatology. Typically, disease progression is more pronounced in patients with early onset of neurological symptoms. Heterogeneous clinical presentation may hinder disease recognition and lead to delays in diagnosis. Here we describe the prevalence of signs and symptoms observed in patients with NP-C and analyse the relationship between these symptoms in different age groups.

METHODS

The combined patient cohort used in the analyses comprised NP-C cases (n=164) and controls (n=135) aged 0 to 60years from two previously published cohorts; a cohort of all ages from which patients ≤4years of age were excluded and a cohort with early-onset NP-C and age-matched controls. The analysis of relationships between different signs and symptoms was performed for both NP-C cases and controls in two sub-groups, ≤4 and >4years of age, using cluster analyses. The threshold of 4years of age was selected to reflect the minimum age cut-off for satisfactory discriminatory power of the original NP-C SI. To assess the prevalence of individual signs and symptoms at age of diagnosis, patients were categorised by age into 5-year sub-groups, and prevalence values estimated for each sign and symptom of NP-C.

RESULTS

Two main clusters of symptoms were clearly defined for NP-C cases in each age sub-group, whereas clusters were not as clearly defined for controls. For NP-C cases ≤4years of age, one cluster comprised exclusively visceral symptoms; the second cluster combined all other signs and symptoms in this age group. For NP-C cases >4years of age, each cluster contained a mixture of visceral, neurological and psychiatric items. Prevalence estimations showed that visceral symptoms (e.g. isolated unexplained splenomegaly) were most common in NP-C cases ≤4years of age. Neurological symptoms were generally more common in NP-C cases >4years of age than in younger patients, with the exception of hypotonia and delayed developmental milestones.

CONCLUSIONS

These analyses provide a comprehensive overview of symptomatology observed in a large combined cohort of patients with NP-C and controls across a wide range of ages. The results largely reflect observations from clinical practice and support the importance of multi-disciplinary approaches for identification of patients with NP-C, taking into account age-specific manifestations and their possible correlations.