Glycoprotein non-metastatic protein B (GPNMB) plasma values in patients with chronic visceral acid sphingomyelinase deficiency.

Acid sphingomyelinase deficiency (ASMD) is a rare LSD characterized by lysosomal accumulation of sphingomyelin, primarily in macrophages. With the recent availability of enzyme replacement therapy, the need for biomarkers to assess severity of disease has increased. Glycoprotein non-metastatic protein B (GPNMB) plasma levels were demonstrated to be elevated in Gaucher disease. Given the similarities between Gaucher disease and ASMD, the hypothesis was that GPNMB might be a potential biochemical marker for ASMD as well. Plasma samples of ASMD patients were analyzed and GPNMB plasma levels were compared to those of healthy volunteers. Visceral disease severity was classified as severe when splenic, hepatic and pulmonary manifestations were all present and as mild to moderate if this was not the case. Median GPNMB levels in 67 samples of 19 ASMD patients were 185 ng/ml (range 70-811 ng/ml) and were increased compared to 10 healthy controls (median 36 ng/ml, range 9-175 ng/ml, p < 0.001). Median plasma GPNMB levels of ASMD patients with mild to moderate visceral disease compared to patients with severe visceral disease differed significantly and did not overlap (respectively 109 ng/ml, range 70-304 ng/ml and 325 ng/ml, range 165-811 ng/ml, p < 0.001). Correlations with other biochemical markers of ASMD (i.e. chitotriosidase activity, CCL18 and lysosphingomyelin, respectively R = 0.28, p = 0.270; R = 0.34, p = 0.180; R = 0.39, p = 0.100) and clinical parameters (i.e. spleen volume, liver volume, diffusion capacity and forced vital capacity, respectively R = 0.59, p = 0.061, R = 0.5, p = 0.100, R = 0.065, p = 0.810, R = -0.38, p = 0.160) could not be established within this study. The results of this study suggest that GPNMB might be suitable as a biomarker of visceral disease severity in ASMD. Correlations between GPNMB and biochemical or clinical markers of ASMD and response to therapy have to be studied in a larger cohort.

Altered Macrophage Function Associated with Crystalline Lung Inflammation in Acid Sphingomyelinase Deficiency.

Deficiency of ASM (acid sphingomyelinase) causes the lysosomal storage Niemann-Pick disease (NPD). Patients with NPD type B may develop progressive interstitial lung disease with frequent respiratory infections. Although several investigations using the ASM-deficient (ASMKO) mouse NPD model revealed inflammation and foamy macrophages, there is little insight into the pathogenesis of NPD-associated lung disease. Using ASMKO mice, we report that ASM deficiency is associated with a complex inflammatory phenotype characterized by marked accumulation of monocyte-derived CD11b+ macrophages and expansion of airspace/alveolar CD11c+ CD11b- macrophages, both with increased size, granularity, and foaminess. Both the alternative and classical pathways were activated, with decreased in situ phagocytosis of opsonized (Fc-coated) targets, preserved clearance of apoptotic cells (efferocytosis), secretion of Th2 cytokines, increased CD11c+/CD11b+ cells, and more than a twofold increase in lung and plasma proinflammatory cytokines. Macrophages, neutrophils, eosinophils, and noninflammatory lung cells of ASMKO lungs also exhibited marked accumulation of chitinase-like protein Ym1/2, which formed large eosinophilic polygonal Charcot-Leyden-like crystals. In addition to providing insight into novel features of lung inflammation that may be associated with NPD, our report provides a novel connection between ASM and the development of crystal-associated lung inflammation with alterations in macrophage biology.

Biochemical and imaging parameters in acid sphingomyelinase deficiency: Potential utility as biomarkers.

Acid Sphingomyelinase Deficiency (ASMD), or Niemann-Pick type A/B disease, is a rare lipid storage disorder leading to accumulation of sphingomyelin and its precursors primarily in macrophages. The disease has a broad phenotypic spectrum ranging from a fatal infantile form with severe neurological involvement (the infantile neurovisceral type) to a primarily visceral form with different degrees of pulmonary, liver, spleen and skeletal involvement (the chronic visceral type). With the upcoming possibility of treatment with enzyme replacement therapy, the need for biomarkers that predict or reflect disease progression has increased. Biomarkers should be validated for their use as surrogate markers of clinically relevant endpoints. In this review, clinically important endpoints as well as biochemical and imaging markers of ASMD are discussed and potential new biomarkers are identified. We suggest as the most promising biomarkers that may function as surrogate endpoints in the future: diffusion capacity measured by spirometry, spleen volume, platelet count, low-density lipoprotein cholesterol, liver fibrosis measured with a fibroscan, lysosphingomyelin and walked distance in six minutes. Currently, no biomarkers have been validated. Several plasma markers of lipid-laden cells, fibrosis or inflammation are of high potential as biomarkers and deserve further study. Based upon current guidelines for biomarkers, recommendations for the validation process are provided.

Niemann-Pick disease type-B: a unique case report with compound heterozygosity and complicated lipid management.

BACKGROUND: Niemann-Pick disease (NPD) is a rare autosomal recessive hereditary disease characterized by deficient activity of acid sphingomyelinase. CASE PRESENTATION: We present a case of NPD type B with a unique compound heterozygosity for SMPD1 (NM_000543.4:c.[84delC];[96G > A]) in which both mutations that induce an early stop codon are located before the second in-frame initiation codon. The clinical presentation of the patient is compatible with NPD type B. She was initially diagnosed of Gaucher Disease, but her altered lipid profile led to a clinical suspicion of NPD. Combined high doses of atorvastatin and ezetimibe were given to treat the severe hypercholesterolemia. CONCLUSIONS: The pharmacological management of the lipid profile in these patients is important. A unique compound mutation in SMPD1 gene is described.

Oral, dental, and craniofacial features in chronic acid sphingomyelinase deficiency.

The aim of this study was to evaluate the oral, dental, and craniofacial features of individuals affected by the chronic forms of acid sphingomyelinase deficiency (ASMD). This study comprised a sample of adult and pediatric patients (n = 8) with chronic ASMD. The individuals underwent oral examinations to evaluate the occurrence of caries, as well as full-mouth periodontal examinations, to assess the occurrence and severity of periodontal diseases. Panoramic and profile radiographs were obtained to analyze dental conditions and craniofacial parameters. Participants also answered questionnaires to identify systemic impairment, parafunctional habits, and bruxism. Dental anomalies of size, shape, and number were found, with agenesis and microdontia being the predominant findings. The average of caries experience was 11.75 (±8.1). Only one patient had periodontal health and all adult individuals had periodontitis at different stages and degrees. Bruxism was found in 87.5% of the sample. The convex profile and maxillary and mandibular retrusion were the most relevant findings in the cephalometric analysis. It is concluded that individuals with chronic ASMD, in addition to several systemic manifestations, present significant modifications in their oral health, from a greater occurrence of dental anomalies, caries, periodontal disease, in addition to skeletal changes.

Solving the secretory acid sphingomyelinase puzzle: Insights from lysosome-mediated parasite invasion and plasma membrane repair.

Acid sphingomyelinase (ASM) is a lysosomal enzyme that cleaves the phosphorylcholine head group of sphingomyelin, generating ceramide. Recessive mutations in SMPD1, the gene encoding ASM, cause Niemann-Pick Disease Types A and B. These disorders are attributed not only to lipid accumulation inside lysosomes but also to changes on the outer leaflet of the plasma membrane, highlighting an extracellular role for ASM. Secretion of ASM occurs under physiological conditions, and earlier studies proposed two forms of the enzyme, one resident in lysosomes and another form that would be diverted to the secretory pathway. Such differential intracellular trafficking has been difficult to explain because there is only one SMPD1 transcript that generates an active enzyme, found primarily inside lysosomes. Unexpectedly, studies of cell invasion by the protozoan parasite Trypanosoma cruzi revealed that conventional lysosomes can fuse with the plasma membrane in response to elevations in intracellular Ca2+ , releasing their contents extracellularly. ASM exocytosed from lysosomes remodels the outer leaflet of the plasma membrane, promoting parasite invasion and wound repair. Here, we discuss the possibility that ASM release during lysosomal exocytosis, in response to various forms of stress, may represent a major source of the secretory form of this enzyme.

Niemann-Pick Disease Type B in Traumatic Splenic Rupture.

The rupture of spleen is common in clinical and forensic practice. Trauma is the most common cause of splenic rupture. Although rare, traumatic splenic rupture may occur in these individuals with asymptomatic underlying disease, and clinical and forensic pathologists may neglect the disease and diagnose only the traumatic splenic rupture. Here, we present a case of postinjury splenic rupture resulting in splenectomy, where the patient was diagnosed with Niemann-Pick disease type B through histopathological examination and genetic testing. In forensic practice, in cases of isolation splenic rupture, full microscopy should be done to differentiate traumatic rupture from a spontaneous bleed due to an underlying disease process.

The Effects of Liver Transplantation in Children With Niemann-Pick Disease Type B.

We evaluated the effects of liver transplantation (LT) in children with Niemann-Pick disease (NPD) type B. From October 2006 to October 2018, 7 of 1512 children who received LT at Ren Ji Hospital were diagnosed as NPD type B. The median age at diagnosis was 12 months (6-14 months) with initial presentations of hepatosplenomegaly, growth retardation, repeated pneumonia, and diarrhea. Even after comprehensive supporting treatments, all patients developed liver dysfunction, severe interstitial pulmonary disease, compromised lung function, and hypersplenism, with hypertriglyceridemia in 4 patients. They were transferred to our hospital for transplantation (median age, 6.5 years; range, 2.2-8.6 years). Among them, 4 patients received living donor LT, and 3 received whole-liver orthotopic LT. Splenectomy was conducted spontaneously. All patients are alive with a median follow-up of 10 months (range, 5-53 months). Liver function normalized within 3 weeks after transplantation and maintained stability. Thrombocytopenia and leukopenia were cured, as was hypertriglyceridemia. Strikingly, pulmonary disease was relieved after transplantation, as evidenced by resolution of interstitial lung disease and restored lung function. Bronchitis occurred only once among the 3 patients with a quick recovery during follow-up. Catch-up growth was observed in all patients, especially in 1 male patient, as his height z score increased from -3.9 to -1 at 4 years after transplantation. Patients with follow-up longer than 10 months indicated significant psychomotor ability improvement. Hypotonia was relieved in 4 patients after transplantation. However, intelligence developmental delay still existed in 4 patients during the follow-up. Three of them have been receiving intelligence recovery therapy, although the longterm effect needs more investigation. In conclusion, LT is a safe and effective treatment for patients with NPD type B with severe liver and pulmonary dysfunction.

Hepatosplenomegaly, pneumopathy, bone changes and fronto-temporal dementia: Niemann-Pick type B and SQSTM1-associated Paget's disease in the same individual.

Data from exome sequencing show that a proportion of individuals in whom a genetic disorder is suspected turn out to have not one, but two to four distinct ones. This may require an evolution in our diagnostic attitude towards individuals with complex disorders. We report a patient with splenomegaly, pneumopathy, bone changes and fronto-temporal dementia (FTD). "Sea-blue histiocytes" in his bone marrow pointed to a lysosomal storage disease. Homozygosity for a pathogenic mutation in the SMPD1 gene confirmed Niemann-Pick disease type B (NPD-B). Mild cognitive impairment and abnormal brain FDG PET were consistent with FTD. We initially tried to fit the skeletal and neurologic phenotype into the NPD-B diagnosis. However, additional studies revealed a pathogenic mutation in the SQSTM1 gene. Thus, our patient had two distinct diseases; NPD-B, and Paget's disease of bone with FTD. The subsequent finding of a mutation in SQSTM1 gene ended our struggle to explain the combination of findings by a singular "unifying" diagnosis and allowed us to make specific therapeutic decisions. SQSTM1 mutations have been reported in association with FTD, possibly because of defective autophagy. Bisphosphonates may be beneficial for PDB, but since they are known to inhibit acid sphingomyelinase activity, we refrained from using them in this patient. While the principle of looking for unifying diagnosis remains valid, physicians should consider the possibility of co-existing multiple diagnoses when clinical features are difficult to explain by a single one. Accurate diagnostic work-up can guide genetic counseling but also lead to better medical management.

Niemann-Pick disease A or B in four pediatric patients and SMPD1 mutation carrier frequency in the Mexican population.

INTRODUCTION AND OBJECTIVES: Niemann-Pick disease type A (NPD-A) and B (NPD-B) are lysosomal storage diseases with a birth prevalence of 0.4-0.6/100,000. They are caused by a deficiency in acid sphingomyelinase, an enzyme encoded by SMPD1. We analyzed the phenotype and genotype of four unrelated Mexican patients, one with NPD-A and three with NPD-B. PATIENTS AND METHODS: Four female patients between 1 and 7 years of age were diagnosed with NPD-A or NPD-B by hepatosplenomegaly, among other clinical characteristics, and by determining the level of acid sphingomyelinase enzymatic activity and sequencing of the SMPD1 gene. Additionally, a 775bp amplicon of SMPD1 (from 11:6393835_6394609, including exons 5 and 6) was analyzed by capillary sequencing in a control group of 50 unrelated healthy Mexican Mestizos. RESULTS: An infrequent variant (c.1343A>G p.Tyr448Cys) was observed in two patients. One is the first NPD-A homozygous patient reported with this variant and the other a compound heterozygous NPD-B patient with the c.1829_1831delGCC p.Arg610del variant. Another compound heterozygous patient had the c.1547A>G p.His516Arg variant (not previously described in affected individuals) along with the c.1805G>A p.Arg602His variant. A new c.1263+8C>T pathogenic variant was encountered in a homozygous state in a NPD-B patient. Among the healthy control individuals there was a heterozygous carrier for the c.1550A>T (rs142787001) pathogenic variant, but none with the known pathogenic variants in the 11:6393835_6394609 region of SMPD1. CONCLUSIONS: The present study provides further NPD-A or B phenotype-genotype correlations. We detected a heterozygous carrier with a pathogenic variant in 1/50 healthy Mexican mestizos.

Multimodal imaging including optical coherence tomography angiography in patients with type B Niemann-Pick disease.

PURPOSE: To evaluate accumulation patterns of deposits in retinal layers of type B Niemann-Pick patients by multimodal imaging. METHODS: Seven patients with type B Niemann-Pick disease were included in this study. All participants underwent a complete ophthalmologic evaluation, high-resolution digital colour imaging, spectral-domain optical coherence tomography, blue light fundus autofluorescence and optical coherence tomography angiography (OCTA). RESULTS: We demonstrated different accumulation patterns in the retinal ganglion cell layer, the retinal nerve fibre layer and the subfoveolar region by multimodal imaging. Local retinal capillary nonflow areas in the superficial plexus, increased vascular tortuosity and deformed foveal avascular areas were shown in OCTA scans. CONCLUSION: Multimodal imaging including OCTA is a useful technique for the identification of different types of accumulation patterns, diagnosis and follow-up of type B Niemann-Pick patients.

Unravelling new pathways of sterol metabolism: lessons learned from in-born errors and cancer.

PURPOSE OF REVIEW: To update researchers of recently discovered metabolites of cholesterol and of its precursors and to suggest relevant metabolic pathways. RECENT FINDINGS: Patients suffering from inborn errors of sterol biosynthesis, transport and metabolism display unusual metabolic pathways, which may be major routes in the diseased state but minor in the healthy individual. Although quantitatively minor, these pathways may still be important in healthy individuals. Four inborn errors of metabolism, Smith-Lemli-Opitz syndrome, cerebrotendinous xanthomatosis and Niemann Pick disease types B (NPB) and C (NPC) result from mutations in different genes but can generate elevated levels of the same sterol metabolite, 7-oxocholesterol, in plasma. How this molecule is metabolized further is of great interest as its metabolites may have an important role in embryonic development. A second metabolite, abundant in NPC and NPB diseases, cholestane-3ß,5α,6ß-triol (3ß,5α,6ß-triol), has recently been shown to be metabolized to the corresponding bile acid, 3ß,5α,6ß-trihydroxycholanoic acid, providing a diagnostic marker in plasma. The origin of cholestane-3ß,5α,6ß-triol is likely to be 3ß-hydroxycholestan-5,6-epoxide, which can alternatively be metabolized to the tumour suppressor dendrogenin A (DDA). In breast tumours, DDA levels are found to be decreased compared with normal tissues linking sterol metabolism to cancer. SUMMARY: Unusual sterol metabolites and pathways may not only provide markers of disease, but also clues towards cause and treatment.

Hematopoietic stem cell transplantation in Niemann-Pick disease type B monitored by chitotriosidase activity.

Here, we report a patient with Niemann-Pick disease type B, with early severe onset of disease and pulmonary involvement, treated with hematopoietic stem cell transplant (HSCT) from a bone marrow matched unrelated donor. We confirm that HSCT is feasible and potentially beneficial for patients with severe phenotype. Noteworthy, we discussed the potential usefulness of the activity of peripheral chitotriosidase for the longitudinal evaluation of HSCT success and effectiveness.

Enhanced Delivery and Effects of Acid Sphingomyelinase by ICAM-1-Targeted Nanocarriers in Type B Niemann-Pick Disease Mice.

Acid sphingomyelinase deficiency in type B Niemann-Pick disease leads to lysosomal sphingomyelin storage, principally affecting lungs, liver, and spleen. Infused recombinant enzyme is beneficial, yet its delivery to the lungs is limited and requires higher dosing than liver and spleen, leading to potentially adverse reactions. Previous studies showed increased enzyme pulmonary uptake by nanocarriers targeted to ICAM-1, a protein overexpressed during inflammation. Here, using polystyrene and poly(lactic-co-glycolic acid) nanocarriers, we optimized lung delivery by varying enzyme dose and nanocarrier concentration, verified endocytosis and lysosomal trafficking in vivo, and evaluated delivered activity and effects. Raising the enzyme load of nanocarriers progressively increased absolute enzyme delivery to all lung, liver, and spleen, over the naked enzyme. Varying nanocarrier concentration inversely impacted lung versus liver and spleen uptake. Mouse intravital and postmortem examination verified endocytosis, transcytosis, and lysosomal trafficking using nanocarriers. Compared to naked enzyme, nanocarriers increased enzyme activity in organs and reduced lung sphingomyelin storage and macrophage infiltration. Although old mice with advanced disease showed reactivity (pulmonary leukocyte infiltration) to injections, including buffer without carriers, antibody, or enzyme, younger mice with mild disease did not. We conclude that anti-ICAM nanocarriers may result in effective lung enzyme therapy using low enzyme doses.

Decreasing SMPD1 activity in BEAS-2B bronchial airway epithelial cells results in increased NRF2 activity, cytokine synthesis and neutrophil recruitment.

Niemann-Pick disease (NPD) type B is a rare autosomal recessive disease characterized by variable levels of impairment in sphingomyelin phosphodiesterase 1 (SMPD1) activity. Lung involvement is the most important prognostic factor in NPD-B, with recurrent respiratory infections starting in infancy being the major cause of morbidity and mortality. We hypothesized that decreased SMPD1 activity impaired airway epithelium host defense response. SMPD1 activity was reduced using inducible shRNA. Surprisingly, decreasing SMPD1 activity by 50%, resulted in increased neutrophil recruitment, both at baseline and in response to bacterial stimulation. This correlated with elevated levels of cytokine mRNA shown to contribute to neutrophil recruitment in unstimulated (e.g. IL-8 and GRO-α) and infected cells (e.g. IL-8, GRO-α, GM-CSF and CCL20). Instead of preventing the host defence responses, decreased SMPD1 activity results in an inflammatory response even in the absence of infection. Moreover, decreasing SMPD1 activity resulted in a pro-oxidative shift. Accordingly, expression of an inactive mutant, SMPD1[L225P] but not the WT enzyme increased activation of the antioxidant transcription factor NRF2. Therefore, decreasing SMPD1 activity by 50% in airway epithelial cells, the equivalent of the loss of one allele, results in the accumulation of oxidants that activates NRF2 and a concomitant increased cytokine production as well as neutrophil recruitment. This can result in a chronic inflammatory state that impairs host defence similar to scenarios observe in other chronic inflammatory lung disease such as Chronic Obstructive Pulmonary Disease or Cystic Fibrosis.

Consensus recommendation for a diagnostic guideline for acid sphingomyelinase deficiency.

Disclaimer:This diagnostic guideline is intended as an educational resource and represents the opinions of the authors, and is not representative of recommendations or policy of the American College of Medical Genetics and Genomics (ACMG). The information should be considered a consensus based on expert opinion, as more comprehensive levels of evidence were not available in the literature in all cases. BACKGROUND: Acid sphingomyelinase deficiency (ASMD) is a rare, progressive, and often fatal lysosomal storage disease. The underlying metabolic defect is deficiency of the enzyme acid sphingomyelinase that results in progressive accumulation of sphingomyelin in target tissues. ASMD manifests as a spectrum of severity ranging from rapidly progressive severe neurovisceral disease that is uniformly fatal to more slowly progressive chronic neurovisceral and chronic visceral forms. Disease management is aimed at symptom control and regular assessments for multisystem involvement. PURPOSE AND METHODS: An international panel of experts in the clinical and laboratory evaluation, diagnosis, treatment/management, and genetic aspects of ASMD convened to review the evidence base and share personal experience in order to develop a guideline for diagnosis of the various ASMD phenotypes. CONCLUSIONS: Although care of ASMD patients is typically provided by metabolic disease specialists, the guideline is directed at a wide range of providers because it is important for primary care providers (e.g., pediatricians and internists) and specialists (e.g., pulmonologists, hepatologists, and hematologists) to be able to identify ASMD.Genet Med advance online publication 13 April 2017.

Quantitation of plasmatic lysosphingomyelin and lysosphingomyelin-509 for differential screening of Niemann-Pick A/B and C diseases.

Acid sphingomyelinase deficiency (ASMd, Niemann-Pick disease A/B) and Niemann-Pick type C disease (NPC) share core clinical symptoms. Initial diagnostic discrimination of these two rare lysosomal storage diseases is thus difficult. As sphingomyelin accumulates in ASMd as well as NPC, lysosphingomyelin (sphingosylphosphorylcholine) and its m/z 509 analog were suggested as biomarkers for both diseases. Herein we present results of simultaneous LC-ESI-MS/MS measurements of lysosphingomyelin and lysosphingomyelin 509 in plasma and dried blood spots (DBS) collected from ASMd and NPC patients and suggest that the plasma but not DBS levels of the two analytes allow differential biochemical screening of ASMd and NPC.

SMPD1 Mutation Update: Database and Comprehensive Analysis of Published and Novel Variants.

Niemann-Pick Types A and B (NPA/B) diseases are autosomal recessive lysosomal storage disorders caused by the deficient activity of acid sphingomyelinase (ASM) because of the mutations in the SMPD1 gene. Here, we provide a comprehensive updated review of already reported and newly identified SMPD1 variants. Among them, 185 have been found in NPA/B patients. Disease-causing variants are equally distributed along the SMPD1 gene; most of them are missense (65.4%) or frameshift (19%) mutations. The most frequently reported mutation worldwide is the p.R610del, clearly associated with an attenuated NP disease type B phenotype. The available information about the impact of 52 SMPD1 variants on ASM mRNA and/or enzymatic activity has been collected and whenever possible, phenotype/genotype correlations were established. In addition, we created a locus-specific database easily accessible at http://www.inpdr.org/genes that catalogs the 417 SMPD1 variants reported to date and provides data on their in silico predicted effects on ASM protein function or mRNA splicing. The information reviewed in this article, providing new insights into the genotype/phenotype correlation, is extremely valuable to facilitate diagnosis and genetic counseling of families affected by NPA/B.

Novel first-dose adverse drug reactions during a phase I trial of olipudase alfa (recombinant human acid sphingomyelinase) in adults with Niemann-Pick disease type B (acid sphingomyelinase deficiency).

PURPOSE: Enzyme replacement therapy with olipudase alfa (recombinant human acid sphingomyelinase) is being developed for Niemann-Pick disease type B (NPD B). METHODS: A single-center, open-label, nonrandomized, single-ascending-dose trial evaluated the safety of intravenous olipudase alfa (0.03-1.0 mg/kg) in 11 adults with NPD B. Patients were monitored in the hospital for 72 h after infusion and had follow-up visits on days 14 and 28. RESULTS: Plasma ceramide, a product of sphingomyelin catabolism by olipudase alfa, showed dose-dependent elevations by 6 h postdose, or postinfusion. No serious adverse drug reactions (ADRs) occurred during the study. Acute phase reaction-type ADRs, as evidenced by elevated inflammatory biomarkers (high-sensitivity C-reactive protein, interleukin-8, and calcitonin) and constitutional symptoms (fever, pain, nausea, and/or vomiting) emerged 12-24 h following doses ≥0.3 mg/kg olipudase alfa. Three patients experienced hyperbilirubinemia. The study was terminated after a patient dosed at 1 mg/kg exhibited severe hyperbilirubinemia; he was subsequently diagnosed with Gilbert syndrome. CONCLUSION: The maximum tolerated dose of olipudase alfa in adults with NPD B was 0.6 mg/kg. First-dose ADRs were likely induced by elevated concentrations of ceramide (or its downstream derivatives) generated by the catabolism of accumulated sphingomyelin. Within-patient dose escalation to slowly catabolize sphingomyelin stores may be a strategy to mitigate first-dose ADRs in patients with NPD B.Genet Med 18 1, 34-40.