Pulmonary involvement in Niemann-Pick C type 1

Peripheral Blood Mononuclear Cell Gene Expression Associated with Pulmonary Microvascular Perfusion: The Multi-Ethnic Study of Atherosclerosis Chronic Obstructive Pulmonary Disease

Rationale: Chronic obstructive pulmonary disease (COPD) and emphysema are associated with endothelial damage and altered pulmonary microvascular perfusion. The molecular mechanisms underlying these changes are poorly understood in patients, in part because of the inaccessibility of the pulmonary vasculature. Peripheral blood mononuclear cells (PBMCs) interact with the pulmonary endothelium. Objectives: To test the association between gene expression in PBMCs and pulmonary microvascular perfusion in COPD. Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited two independent samples of COPD cases and controls with ⩾10 pack-years of smoking history. In both samples, pulmonary microvascular blood flow, pulmonary microvascular blood volume, and mean transit time were assessed on contrast-enhanced magnetic resonance imaging, and PBMC gene expression was assessed by microarray. Additional replication was performed in a third sample with pulmonary microvascular blood volume measures on contrast-enhanced dual-energy computed tomography. Differential expression analyses were adjusted for age, gender, race/ethnicity, educational attainment, height, weight, smoking status, and pack-years of smoking. Results: The 79 participants in the discovery sample had a mean age of 69 ± 6 years, 44% were female, 25% were non-White, 34% were current smokers, and 66% had COPD. There were large PBMC gene expression signatures associated with pulmonary microvascular perfusion traits, with several replicated in the replication sets with magnetic resonance imaging (n = 47) or dual-energy contrast-enhanced computed tomography (n = 157) measures. Many of the identified genes are involved in inflammatory processes, including nuclear factor-κB and chemokine signaling pathways. Conclusions: PBMC gene expression in nuclear factor-κB, inflammatory, and chemokine signaling pathways was associated with pulmonary microvascular perfusion in COPD, potentially offering new targetable candidates for novel therapies.

The Genetic Basis, Lung Involvement, and Therapeutic Options in Niemann-Pick Disease: A Comprehensive Review

Niemann-Pick Disease (NPD) is a rare autosomal recessive disease belonging to lysosomal storage disorders. Three types of NPD have been described: NPD type A, B, and C. NPD type A and B are caused by mutations in the gene SMPD1 coding for sphingomyelin phosphodiesterase 1, with a consequent lack of acid sphingomyelinase activity. These diseases have been thus classified as acid sphingomyelinase deficiencies (ASMDs). NPD type C is a neurologic disorder due to mutations in the genes NPC1 or NPC2, causing a defect of cholesterol trafficking and esterification. Although all three types of NPD can manifest with pulmonary involvement, lung disease occurs more frequently in NPD type B, typically with interstitial lung disease, recurrent pulmonary infections, and respiratory failure. In this sense, bronchoscopy with broncho-alveolar lavage or biopsy together with high-resolution computed tomography are fundamental diagnostic tools. Although several efforts have been made to find an effective therapy for NPD, to date, only limited therapeutic options are available. Enzyme replacement therapy with Olipudase α is the first and only approved disease-modifying therapy for patients with ASMD. A lung transplant and hematopoietic stem cell transplantation are also described for ASMD in the literature. The only approved disease-modifying therapy in NPD type C is miglustat, a substrate-reduction treatment. The aim of this review was to delineate a state of the art on the genetic basis and lung involvement in NPD, focusing on clinical manifestations, radiologic and histopathologic characteristics of the disease, and available therapeutic options, with a gaze on future therapeutic strategies.

Potential Composite Digenic Contribution of NPC1 and NOD2 Leading to Atypical Lethal Niemann-Pick Type C with Initial Crohn’s Disease-like Presentation: Genotype-Phenotype Correlation Study

Niemann–Pick disease type C (NPC) is an autosomal recessive neurovisceral disease characterized by progressive neurodegeneration with variable involvement of multisystemic abnormalities. Crohn’s disease (CD) is an inflammatory bowel disease (IBD) with a multifactorial etiology influenced by variants in NOD2. Here, we investigated a patient with plausible multisystemic overlapping manifestations of both NPC and CD. Her initial hospitalization was due to a prolonged fever and non-bloody diarrhea. A few months later, she presented with recurrent skin tags and anal fissures. Later, her neurological and pulmonary systems progressively deteriorated, leading to her death at the age of three and a half years. Differential diagnosis of her disease encompassed a battery of clinical testing and genetic investigations. The patient’s clinical diagnosis was inconclusive. Specifically, the histopathological findings were directed towards an IBD disease. Nevertheless, the diagnosis of IBD was not consistent with the patient’s subsequent neurological and pulmonary deterioration. Consequently, we utilized a genetic analysis approach to guide the diagnosis of this vague condition. Our phenotype–genotype association attempts led to the identification of candidate disease-causing variants in both NOD2 and NPC1. In this study, we propose a potential composite digenic impact of these two genes as the underlying molecular etiology. This work lays the foundation for future functional and mechanistic studies to unravel the digenic role of NOD2 and NPC1.

Elevated Alpha-Fetoprotein in Infantile-Onset Niemann-Pick Type C Disease with Liver Involvement

Niemann-Pick disease type C (NPC) is a rare autosomal recessive neuro-visceral lipid storage disease. We describe nine cases of infantile-onset NPC with various genetic mutations in the NPC1 gene, which presented with neonatal cholestasis. Serum alpha-fetoprotein (AFP) levels were obtained as part of their workup during the first four months of life. In eight of nine (89%) patients, serum AFP demonstrated elevated levels. Seven infants displayed marked elevations, ranging from 4 to 300 times the upper limit for age-adjusted norms. In most patients, AFP levels peaked during the initial test and declined over time as cholestasis resolved. We conclude that elevated AFP levels are a common, although non-specific, marker for NPC-associated liver disease. These findings demonstrate the benefit of including AFP levels in the workup of neonatal liver disease, especially if there is accompanied cholestasis and if NPC is suspected.

iPS-derived neural stem cells for disease modeling and evaluation of therapeutics for mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a rare, lysosomal disorder caused by mutations in a gene encoding iduronate-2-sulfatase (IDS). IDS deficiency results in an accumulation of glycosaminoglycans (GAGs) and secondary accumulations of other lipids in lysosomes. Symptoms of MPS II include a variety of soft and hard tissue problems, developmental delay, and deterioration of multiple organs. Enzyme replacement therapy is an approved treatment for MPS II, but fails to improve neuronal symptoms. Cell-based neuronal models of MPS II disease are needed for compound screening and drug development for the treatment of the neuronal symptoms in MPS II. In this study, three induced pluripotent stem cell (iPSC) lines were generated from three MPS II patient-derived dermal fibroblast cell lines that were differentiated into neural stem cells and neurons. The disease phenotypes were measured using immunofluorescence staining and Nile red dye staining. In addition, the therapeutic effects of recombinant human IDS enzyme, delta-tocopherol (DT), and hydroxypropyl-beta-cyclodextrin (HPBCD) were determined in the MPS II disease cells. Finally, the neural stem cells from two of the MPS II iPSC lines exhibited typical disease features including a deficiency of IDS activity, abnormal glycosaminoglycan storage, and secondary lipid accumulation. Enzyme replacement therapy partially rescued the disease phenotypes in these cells. DT showed a significant effect in reducing the secondary accumulation of lipids in the MPS II neural stem cells. In contrast, HPBCD displayed limited or no effect in these cells. Our data indicate that these MPS II cells can be used as a cell-based disease model to study disease pathogenesis, evaluate drug efficacy, and screen compounds for drug development.

Normal long-term neurologic and graft outcome after liver transplantation in an infant with Neimann-Pick type C disease

Niemann-Pick type C disease is a rare autosomal recessive lysosomal disorder that leads to the accumulation of lipids in cellular organelles. Affected infants are often cholestatic with hepatosplenomegaly, developmental delay and may present in acute liver failure. Medical therapy has shown some promise in long-term studies, in patients with milder phenotypes of the disease. Liver transplantation has generally not been considered a therapeutic option due to the systemic nature of the condition, and frequent unremitting neurological decline leading to death. We report an infant with multisystem organ failure, and known Niemann-Pick C disease who was successfully transplanted and has maintained normal neurological outcomes now five years after transplantation. We highlight the need for multidisciplinary care in order to recognize different phenotypes that may exist, even in rare diseases, and to be aware of evolving therapeutic options.

Endolysosomal Cation Channels and Lung Disease

Endolysosomal cation channels are emerging as key players of endolysosomal function such as endolysosomal trafficking, fusion/fission, lysosomal pH regulation, autophagy, lysosomal exocytosis, and endocytosis. Diseases comprise lysosomal storage disorders (LSDs) and neurodegenerative diseases, metabolic diseases, pigmentation defects, cancer, immune disorders, autophagy related diseases, infectious diseases and many more. Involvement in lung diseases has not been a focus of attention so far but recent developments in the field suggest critical functions in lung physiology and pathophysiology. Thus, loss of TRPML3 was discovered to exacerbate emphysema formation and cigarette smoke induced COPD due to dysregulated matrix metalloproteinase 12 (MMP-12) levels in the extracellular matrix of the lung, a known risk factor for emphysema/COPD. While direct lung function measurements with the exception of TRPML3 are missing for other endolysosomal cation channels or channels expressed in lysosome related organelles (LRO) in the lung, links between those channels and important roles in lung physiology have been established such as the role of P2X4 in surfactant release from alveolar epithelial Type II cells. Other channels with demonstrated functions and disease relevance in the lung such as TRPM2, TRPV2, or TRPA1 may mediate their effects due to plasma membrane expression but evidence accumulates that these channels might also be expressed in endolysosomes, suggesting additional and/or dual roles of these channels in cell and intracellular membranes. We will discuss here the current knowledge on cation channels residing in endolysosomes or LROs with respect to their emerging roles in lung disease.

Channels and Transporters of the Pulmonary Lamellar Body in Health and Disease

The lamellar body (LB) of the alveolar type II (ATII) cell is a lysosome-related organelle (LRO) that contains surfactant, a complex mix of mainly lipids and specific surfactant proteins. The major function of surfactant in the lung is the reduction of surface tension and stabilization of alveoli during respiration. Its lack or deficiency may cause various forms of respiratory distress syndrome (RDS). Surfactant is also part of the innate immune system in the lung, defending the organism against air-borne pathogens. The limiting (organelle) membrane that encloses the LB contains various transporters that are in part responsible for translocating lipids and other organic material into the LB. On the other hand, this membrane contains ion transporters and channels that maintain a specific internal ion composition including the acidic pH of about 5. Furthermore, P2X4 receptors, ligand gated ion channels of the danger signal ATP, are expressed in the limiting LB membrane. They play a role in boosting surfactant secretion and fluid clearance. In this review, we discuss the functions of these transporting pathways of the LB, including possible roles in disease and as therapeutic targets, including viral infections such as SARS-CoV-2.

Transcriptome of HPβCD-treated Niemann-pick disease type C1 cells highlights GPNMB as a biomarker for therapeutics

The rare, fatal neurodegenerative disorder Niemann-Pick disease type C1 (NPC1) arises from lysosomal accumulation of unesterified cholesterol and glycosphingolipids. These subcellular pathologies lead to phenotypes of hepatosplenomegaly, neurological degeneration and premature death. The timing and severity of NPC1 clinical presentation is extremely heterogeneous. This study analyzed RNA-Seq data from 42 NPC1 patient-derived, primary fibroblast cell lines to determine transcriptional changes induced by treatment with 2-hydroxypropyl-β-cyclodextrin (HPβCD), a compound currently under investigation in clinical trials. A total of 485 HPβCD-responsive genes were identified. Pathway enrichment analysis of these genes showed significant involvement in cholesterol and lipid biosynthesis. Furthermore, immunohistochemistry of the cerebellum as well as measurements of serum from Npc1m1N null mice treated with HPβCD and adeno-associated virus (AAV) gene therapy suggests that one of the identified genes, GPNMB, may serve as a useful biomarker of treatment response in NPC1 disease. Overall, this large NPC1 patient-derived dataset provides a comprehensive foundation for understanding the genomic response to HPβCD treatment.

[Neonatal-onset Niemann-Pick type C disease with COVID-19 infection]

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Gene Therapy in a Mouse Model of Niemann-Pick Disease Type C1

Niemann–Pick disease type C1 (NPC1) is a fatal congenital neurodegenerative disorder caused by mutations in the NPC1 gene, which is involved in cholesterol transport in lysosomes. Broad clinical manifestations of NPC1 include liver failure, pulmonary disorder, neurological deficits, and psychiatric symptoms. The main cause of death in NPC1 patients involves central nervous system (CNS) dysfunction; there is no essential treatment. We generated a tyrosine-mutant adeno-associated virus (AAV) 9/3 vector that expresses human NPC1 under a cytomegalovirus (CMV) promoter (AAV-CMV-hNPC1) and injected it into the left lateral ventricle (5 μL) and cisterna magna (10 μL) of Npc1 homo-knockout (Npc1^−/−) mice. Each mouse received total 1.35 × 10¹¹ vector genome on days 4 or 5 of life. AAV-treated Npc1^−/− mice (n = 11) had an average survival of >28 weeks, while all saline-treated Npc1^−/− mice (n = 11) and untreated Npc1^−/− mice (n = 6) died within 16 weeks. Saline-treated and untreated Npc1^−/− mice lost body weight from 7 weeks until death. However, the average body weight of AAV-treated Npc1^−/− mice increased until 15 weeks. AAV-treated Npc1^−/− mice also showed a significant improvement in the rotarod test performance. A pathological analysis at 11 weeks showed that cerebellar Purkinje cells were preserved in AAV-treated Npc1^−/− mice. In contrast, untreated Npc1^−/− mice showed an almost total loss of cerebellar Purkinje cells. Combined injection into both the lateral ventricle and cisterna magna achieved broader delivery of the vector to the CNS, leading to better outcomes than noted in previous reports, with injection into the lateral ventricles or veins alone. In AAV-treated Npc1^−/− mice, vector genome DNA was detected widely in the CNS and liver. Human NPC1 RNA was detected in the brain, liver, lung, and heart. Accumulated unesterified cholesterol in the liver was reduced in the AAV-treated Npc1^−/− mice. Our results suggest the feasibility of gene therapy for patients with NPC1.

Understanding and Treating Niemann-Pick Type C Disease: Models Matter

Biomedical research aims to understand the molecular mechanisms causing human diseases and to develop curative therapies. So far, these goals have been achieved for a small fraction of diseases, limiting factors being the availability, validity, and use of experimental models. Niemann–Pick type C (NPC) is a prime example for a disease that lacks a curative therapy despite substantial breakthroughs. This rare, fatal, and autosomal-recessive disorder is caused by defects in NPC1 or NPC2. These ubiquitously expressed proteins help cholesterol exit from the endosomal–lysosomal system. The dysfunction of either causes an aberrant accumulation of lipids with patients presenting a large range of disease onset, neurovisceral symptoms, and life span. Here, we note general aspects of experimental models, we describe the line-up used for NPC-related research and therapy development, and we provide an outlook on future topics.

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.

Dietary plant stanol ester supplementation reduces peripheral symptoms in a mouse model of Niemann-Pick type C1 disease

Niemann-Pick type C (NPC)1 disease is a rare genetic condition in which the function of the lysosomal cholesterol transporter NPC1 protein is impaired. Consequently, sphingolipids and cholesterol accumulate in lysosomes of all tissues, triggering a cascade of pathological events that culminate in severe systemic and neurological symptoms. Lysosomal cholesterol accumulation is also a key factor in the development of atherosclerosis and NASH. In these two metabolic diseases, the administration of plant stanol esters has been shown to ameliorate cellular cholesterol accumulation and inflammation. Given the overlap of pathological mechanisms among atherosclerosis, NASH, and NPC1 disease, we sought to investigate whether dietary supplementation with plant stanol esters improves the peripheral features of NPC1 disease. To this end, we used an NPC1 murine model featuring a Npc1-null allele (Npc1nih ), creating a dysfunctional NPC1 protein. Npc1nih mice were fed a 2% or 6% plant stanol ester-enriched diet over the course of 5 weeks. During this period, hepatic and blood lipid and inflammatory profiles were assessed. Npc1nih mice fed the plant stanol-enriched diet exhibited lower hepatic cholesterol accumulation, damage, and inflammation than regular chow-fed Npc1nih mice. Moreover, plant stanol consumption shifted circulating T-cells and monocytes in particular toward an anti-inflammatory profile. Overall, these effects were stronger following dietary supplementation with 6% stanols, suggesting a dose-dependent effect. The findings of our study highlight the potential use of plant stanols as an affordable complementary means to ameliorate disorders in hepatic and blood lipid metabolism and reduce inflammation in NPC1 disease.

Ontogenesis and Modulation of Intestinal Unesterified Cholesterol Sequestration in a Mouse Model of Niemann-Pick C1 Disease

BACKGROUND

Mutations in the NPC1 gene result in sequestration of unesterified cholesterol (UC) and glycosphingolipids in most tissues leading to multi-organ disease, especially in the brain, liver, lungs, and spleen. Various data from NPC1-deficient mice suggest the small intestine (SI) is comparatively less affected, even in late stage disease.

METHODS

Using the Npc1nih mouse model, we measured SI weights and total cholesterol (TC) levels in Npc1-/- versus Npc1+/+ mice as a function of age, and then after prolonged ezetimibe-induced inhibition of cholesterol absorption. Next, we determined intestinal levels of UC and esterified cholesterol (EC), and cholesterol synthesis rates in Npc1-/- and Npc1+/+ mice, with and without the cholesterol-esterifying enzyme SOAT2, following a once-only subcutaneous injection with 2-hydroxypropyl-β-cyclodextrin (2HPβCD).

RESULTS

By ~ 42 days of age, intestinal TC levels averaged ~ 2.1-fold more (mostly UC) in the Npc1-/- versus Npc1+/+ mice with no further increase thereafter. Chronic ezetimibe treatment lowered intestinal TC levels in the Npc1-/- mice by only ~ 16%. In Npc1-/- mice given 2HPβCD 24 h earlier, UC levels fell, EC levels increased (although less so in mice lacking SOAT2), and cholesterol synthesis was suppressed equally in the Npc1-/-:Soat2+/+ and Npc1-/-:Soat2-/- mice.

CONCLUSIONS

The low and static levels of intestinal UC sequestration in Npc1-/- mice likely reflect the continual sloughing of cells from the mucosa. This sequestration is blunted by about the same extent following a single acute treatment with 2HPβCD as it is by a prolonged ezetimibe-induced block of cholesterol absorption.

NPC1 Deficiency in Mice is Associated with Fetal Growth Restriction, Neonatal Lethality and Abnormal Lung Pathology

The rare lysosomal storage disorder Niemann-Pick disease type C1 (NPC1) arises from mutation of NPC1, which encodes a lysosomal transmembrane protein essential for normal transport and trafficking of cholesterol and sphingolipids. NPC1 is highly heterogeneous in both clinical phenotypes and age of onset. Previous studies have reported sub-Mendelian survival rates for mice homozygous for various Npc1 mutant alleles but have not studied the potential mechanisms underlying this phenotype. We performed the first developmental analysis of a Npc1 mouse model, Npc1^em1Pav, and discovered significant fetal growth restriction in homozygous mutants beginning at E16.5. Npc1^{em1Pav/em1Pav} mice also exhibited cyanosis, increased respiratory effort, and over 50% lethality at birth. Analysis of neonatal lung tissues revealed lipid accumulation, notable abnormalities in surfactant, and enlarged alveolar macrophages, suggesting that lung abnormalities may be associated with neonatal lethality in Npc1^{em1Pav/em1Pav} mice. The phenotypic severity of the Npc1^em1Pav model facilitated this first analysis of perinatal lethality and lung pathology in an NPC1 model organism, and this model may serve as a useful resource for developing treatments for respiratory complications seen in NPC1 patients.

Respiratory complications of metabolic disease in the paediatric population: A review of presentation, diagnosis and therapeutic options

Inborn errors of metabolism (IEMs) whilst individually rare, as a group constitute a field which is increasingly demands on pulmonologists. With the advent of new therapies such as enzyme replacement and gene therapy, early diagnosis and treatment of these conditions can impact on long term outcome, making their timely recognition and appropriate investigation increasingly important. Conversely, with improved treatment, survival of these patients is increasing, with the emergence of previously unknown respiratory phenotypes. It is thus important that pulmonologists are aware of and appropriately monitor and manage these complications. This review aims to highlight the respiratory manifestations which can occur. It isdivided into conditions resulting primarily in obstructive airway and lung disease, restrictive lung disease such as interstitial lung disease or pulmonary alveolar proteinosis and pulmonary hypertension, whilst acknowledging that some diseases have the potential to cause all three. The review focuses on general phenotypes of IEMs, their known respiratory complications and the basic metabolic investigations which should be performed where an IEM is suspected.

Expanded access with intravenous hydroxypropyl-β-cyclodextrin to treat children and young adults with Niemann-Pick disease type C1: a case report analysis

Background

Niemann-Pick Disease Type C (NPC) is an inherited, often fatal neurovisceral lysosomal storage disease characterized by cholesterol accumulation in every cell with few known treatments. Defects in cholesterol transport cause sequestration of unesterified cholesterol within the endolysosomal system. The discovery that systemic administration of hydroxypropyl-beta cyclodextrin (HPβPD) to NPC mice could release trapped cholesterol from lysosomes, normalize cholesterol levels in the liver, and prolong life, led to expanded access use in NPC patients. HPβCD has been administered to NPC patients with approved INDs globally since 2009.

Results

Here we present safety, tolerability and efficacy data from 12 patients treated intravenously (IV) for over 7 years with HPβCD in the US and Brazil. Some patients subsequently received intrathecal (IT) treatment with HPβCD following on average 13 months of IV HPβCD. Several patients transitioned to an alternate HPβCD. Moderately affected NPC patients treated with HPβCD showed slowing of disease progression. Severely affected patients demonstrated periods of stability but eventually showed progression of disease. Neurologic and neurocognitive benefits were seen in most patients with IV alone, independent of the addition of IT administration. Physicians and caregivers reported improvements in quality of life for the patients on IV therapy. There were no safety issues, and the drug was well tolerated and easy to administer.

Conclusions

These expanded access data support the safety and potential benefit of systemic IV administration of HPβCD and provide a platform for two clinical trials to study the effect of intravenous administration of HPβCD in NPC patients.

Current Challenges in Understanding the Cellular and Molecular Mechanisms in Niemann-Pick Disease Type C1

Rare diseases are a heterogeneous group of very different clinical syndromes. Their most common causes are defects in the hereditary material, and they can therefore be passed on to descendants. Rare diseases become manifest in almost all organs and often have a systemic expressivity, i.e., they affect several organs simultaneously. An effective causal therapy is often not available and can only be developed when the underlying causes of the disease are understood. In this review, we focus on Niemann–Pick disease type C1 (NPC1), which is a rare lipid-storage disorder. Lipids, in particular phospholipids, are a major component of the cell membrane and play important roles in cellular functions, such as extracellular receptor signaling, intracellular second messengers and cellular pressure regulation. An excessive storage of fats, as seen in NPC1, can cause permanent damage to cells and tissues in the brain and peripheral nervous system, but also in other parts of the body. Here, we summarize the impact of NPC1 pathology on several organ systems, as revealed in experimental animal models and humans, and give an overview of current available treatment options.

Respiratory manifestations in inherited metabolic diseases: 6-year single-center experience

OBJECTIVES

We aimed to call attention to respiratory system manifestations which occur in the course of many inherited metabolic diseases (IMD), and present as the leading cause of death.

MATERIALS AND METHODS

We retrospectively reviewed the diagnosis, treatment, and outcome of patients evaluated at our hospital between June 2012 and June 2018 with a diagnosis of IMD and accompanying respiratory manifestations.

RESULTS

A total of 50 children (29 [58%] male, 21 [42%] female) with IMD and respiratory manifestations were defined. Disorders of intracellular metabolism (n = 33, 66%) formed the majority, followed by intoxication type metabolic disorders (n = 9, 18%) and energy metabolism disorders (n = 8, 16%). The most frequent respiratory symptoms were snoring (20, 40%), tachypnea (16, 32%) and wheezing (14, 28%). Physical examination findings were signs of respiratory distress (n = 28, 56%), crackles (n = 24, 48%), thoracic deformity (n = 23, 46%), decreased breath sounds (n = 17, 34%), rhonchus (n = 17, 34%), wheezing (n = 17, 34%) and stridor (n = 10, 20%). Major respiratory manifestations were chronic airway aspiration (n = 23, 46%), upper airway obstruction (n = 23, 46%), and recurrent pneumonia (n = 18, 36%). Twenty-three 23 patients (46%) experienced endotracheal intubation, 9 patients (18%) required whole-house mechanical ventilation and tonsilloadenoidectomy was performed in 7 patients (14%). Overall survival rate was 70% (n = 35) in a median follow-up period of 2.36 (0.05-5.86) years.

CONCLUSIONS

Respiratory system manifestations of IMD strongly relate with increased morbidity and mortality. Therefore, prompt diagnosis and correct intervention of respiratory complications with a multidisciplinary team including pediatric metabolic diseases specialists, pulmonologists, otorhinolaryngologists, physiotherapists, and anesthesiologists are crucial to prevent progression and irreversible damage.

Molecular Pathways and Respiratory Involvement in Lysosomal Storage Diseases

Lysosomal storage diseases (LSD) include a wide range of different disorders with variable degrees of respiratory system involvement. The purpose of this narrative review is to treat the different types of respiratory manifestations in LSD, with particular attention being paid to the main molecular pathways known so far to be involved in the pathogenesis of the disease. A literature search was conducted using the Medline/PubMed and EMBASE databases to identify studies, from 1968 through to November 2018, that investigated the respiratory manifestations and molecular pathways affected in LSD. Pulmonary involvement includes interstitial lung disease in Gaucher’s disease and Niemann-Pick disease, obstructive airway disease in Fabry disease and ventilatory disorders with chronic respiratory failure in Pompe disease due to diaphragmatic and abdominal wall muscle weakness. In mucopolysaccharidosis and mucolipidoses, respiratory symptoms usually manifest early in life and are secondary to anatomical malformations, particularly of the trachea and chest wall, and to accumulation of glycosaminoglycans in the upper and lower airways, causing, for example, obstructive sleep apnea syndrome. Although the molecular pathways involved vary, ranging from lipid to glycogen and glycosaminoglycans accumulation, some clinical manifestations and therapeutic approaches are common among diseases, suggesting that lysosomal storage and subsequent cellular toxicity are the common endpoints.