Niemann-Pick disease type B: HRCT assessment of pulmonary involvement

Syndromic genetic causes of pulmonary fibrosis

PURPOSE OF REVIEW

The identification of extra-pulmonary symptoms plays a crucial role in diagnosing interstitial lung disease (ILD). These symptoms not only indicate autoimmune diseases but also hint at potential genetic disorders, suggesting a potential overlap between genetic and autoimmune origins.

RECENT FINDINGS

Genetic factors contributing to ILD are predominantly associated with telomere (TRG) and surfactant-related genes. While surfactant-related gene mutations typically manifest with pulmonary involvement alone, TRG mutations were initially linked to syndromic forms of pulmonary fibrosis, known as telomeropathies, which may involve hematological and hepatic manifestations with variable penetrance. Recognizing extra-pulmonary signs indicative of telomeropathy should prompt the analysis of TRG mutations, the most common genetic cause of familial pulmonary fibrosis. Additionally, various genetic diseases causing ILD, such as alveolar proteinosis, alveolar hemorrhage, or unclassifiable pulmonary fibrosis, often present as part of syndromes that include hepatic, hematological, or skin disorders.

SUMMARY

This review explores the main genetic conditions identified over the past two decades.

Lung Diseases and Rare Disorders: Is It a Lysosomal Storage Disease? Differential Diagnosis, Pathogenetic Mechanisms and Management

Pulmonologists may be involved in managing pulmonary diseases in children with complex clinical pictures without a diagnosis. Moreover, they are routinely involved in the multidisciplinary care of children with rare diseases, at baseline and during follow-up, for lung function monitoring. Lysosomal storage diseases (LSDs) are a group of genetic diseases characterised by a specific lysosomal enzyme deficiency. Despite varying pathogen and organ involvement, they are linked by the pathological accumulation of exceeding substrates, leading to cellular toxicity and subsequent organ damage. Less severe forms of LSDs can manifest during childhood or later in life, sometimes being underdiagnosed. Respiratory impairment may stem from different pathogenetic mechanisms, depending on substrate storage in bones, with skeletal deformity and restrictive pattern, in bronchi, with obstructive pattern, in lung interstitium, with altered alveolar gas exchange, and in muscles, with hypotonia. This narrative review aims to outline different pulmonary clinical findings and a diagnostic approach based on key elements for differential diagnosis in some treatable LSDs like Gaucher disease, Acid Sphingomyelinase deficiency, Pompe disease and Mucopolysaccharidosis. Alongside their respiratory clinical aspects, which might overlap, we will describe radiological findings, lung functional patterns and associated symptoms to guide pediatric pulmonologists in differential diagnosis. The second part of the paper will address follow-up and management specifics. Recent evidence suggests that new therapeutic strategies play a substantial role in preventing lung involvement in early-treated patients and enhancing lung function and radiological signs in others. Timely diagnosis, driven by clinical suspicion and diagnostic workup, can help in treating LSDs effectively.

Expert opinion on patient journey, diagnosis and clinical monitoring in acid sphingomyelinase deficiency in Turkey: a pediatric metabolic disease specialist's perspective

This review by a panel of pediatric metabolic disease specialists aimed to provide a practical and implementable guidance document to assist clinicians in best clinical practice in terms of recognition, diagnosis and management of patients with acid sphingomyelinase deficiency (ASMD). The participating experts consider the clinical suspicion of ASMD by the physician to be of utmost importance in the prevention of diagnostic delay and strongly suggest the use of a diagnostic algorithm including/starting with dried blood spots assay in the timely diagnosis of ASMD in patients presenting with hepatosplenomegaly and a need for increased awareness among physicians in this regard to consider ASMD in the differential diagnosis. In anticipation of the introduction of enzyme replacement therapy, raising awareness of the disease among physicians to prevent diagnostic delay and further investigation addressing natural history of ASMD across the disease spectrum, potential presenting characteristics with a high index of suspicion, as well as biomarkers and genotype-phenotype correlations suggestive of poor prognosis seem important in terms of implementation of best practice patterns.

Long-term safety and clinical outcomes of olipudase alfa enzyme replacement therapy in pediatric patients with acid sphingomyelinase deficiency: two-year results

BACKGROUND

Olipudase alfa is a recombinant human acid sphingomyelinase (ASM) enzyme replacement therapy (ERT) for non-central-nervous-system manifestations of acid sphingomyelinase deficiency (ASMD). We report 2-year cumulative safety and efficacy data after olipudase alfa treatment in 20 children (four adolescents [12-17 year], nine children [6-11 year], and seven infants/early child [1-5 year]) with baseline splenomegaly and growth deficits who completed the 1-year ASCEND-Peds clinical trial (NCT02292654) and who continue to receive olipudase alfa in a long-term study (NCT02004704). Efficacy endpoints include spleen and liver volumes, diffusing capacity of the lung for carbon monoxide (DL_CO), high-resolution computed tomography (HRCT) lung imaging, lipid profiles, liver function tests, and height Z-scores.

RESULTS

All 20 former ASCEND-Peds patients completed at least 2 years of olipudase alfa treatment. No patient discontinued and no new safety issue arose during the second year of treatment; 99% of adverse events were mild or moderate. During year 2, one patient had two treatment-related serious events of hypersensitivity that resolved. Mean reductions from baseline in spleen and liver volumes were 61% and 49%, respectively (p < 0.0001) and mean percent-predicted-DL_CO increased by 46.6% (p < 0.0001) in nine patients who performed the test at baseline. Lipid profiles and elevated liver transaminase levels that improved or normalized by 1 year remained stable. Mean height Z-scores improved in all age groups (mean change from baseline 1.17, P < 0.0001).

CONCLUSION

Olipudase alfa was generally well-tolerated during 2 years of treatment. Improvements in clinically relevant disease endpoints observed during the first year of treatment were maintained or augmented in the second year. Trial registration NCT02004704 registered 26 Nov 2013, https://clinicaltrials.gov/ct2/show/record/NCT02004704 .

Prospective study of the natural history of chronic acid sphingomyelinase deficiency in children and adults: eleven years of observation

Background

Acid sphingomyelinase deficiency (ASMD) (also known as Niemann-Pick disease types A and B) is a rare and debilitating lysosomal storage disorder. This prospective, multi-center, multinational longitudinal study aimed to characterize the clinical features of chronic forms of ASMD and disease burden over time in children and adults.

Results

Fifty-nine patients (31 males/28 females) ranging in age from 7 to 64 years with chronic ASMD types A/B and B and at least two disease symptoms participated from 5 countries. Disease characteristics were assessed at baseline, after 1 year, and at the final visit (ranging from 4.5 to 11 years). Thirty patients (51%) were < 18 years at baseline (median age 12 years), and 29 were adults (median age 32 years). Overall, 32/59 patients completed the final visit, 9 died, 9 discontinued, and 9 were lost to follow up. Common clinical characteristics that tended to worsen gradually with time were splenomegaly, hepatomegaly, interstitial lung disease, lung diffusion capacity (DL_CO), and dyslipidemia. Spleen volumes ranged from 4 to 29 multiples of normal at baseline, and splenomegaly was moderate or severe in 86%, 83%, and 90% of individuals at baseline, year 1, and final visits, respectively. The proportion of all individuals with interstitial lung disease was 66% (39/59) at baseline and 78% (25/32) at the final visit, while median % predicted DL_CO decreased by > 10% from baseline to the final visit. Nine patients died (15%), eight of causes related to ASMD (most commonly pneumonia); of these eight patients, five (63%) had symptom onset at or before age 2. Overall, six of the nine deaths occurred before age 50 with three occurring before age 20. Individuals with either severe splenomegaly or prior splenectomy were ten times more likely to have died during the follow-up period than those with smaller or intact spleens (odds ratio 10.29, 95% CI 1.7, 62.7). Most children had growth deficits that persisted into adulthood.

Conclusions

This study provides important information about the natural history of chronic ASMD and provides a longitudinal view of the spectrum of disease manifestations and major morbidities in children and adults and supports the selection of clinically meaningful endpoints in therapeutic trials.

Interstitial lung disease in lysosomal storage disorders

Lysosomes are intracellular organelles that are responsible for degrading and recycling macromolecules. Lysosomal storage diseases (LSDs) are a group of inherited diseases caused by mutations affecting genes that encode the function of the lysosomal enzymes. Three LSDs are associated with lung involvement and/or interstitial lung disease (ILD): Gaucher disease (GD); Niemann-Pick disease, also known as acid sphingomyelinase deficiency (ASMD); and Fabry disease (FD). In GD and in ASMD, analysis of bronchoalveolar lavage fluid and lung biopsy can be informative, showing foamy cells. In GD, ILD is rare. Enzyme replacement therapy (ERT) has been available since 1991 and has greatly changed the natural history of GD, with pulmonary failure and death reported before the ERT era. In ASMD, ILD is frequent and is usually associated with spleen enlargement, low platelet cell count and low level of high-density lipoprotein-cholesterol. Results of ERT are promising regarding preliminary results of olipudase alfa in paediatric and adult ASMD populations. The most frequent respiratory manifestation in FD is COPD-like symptoms regardless of smoking habit and dyspnoea due to congestive heart failure. Early diagnosis of these three LSDs is crucial to prevent irreversible organ damage. Early initiation of ERT can, at least in part, prevent organ failure.

Hepatopulmonary Syndrome and Multiple Arteriovenous Fistulas in a Child with Niemann-Pick Disease

Background: Niemann-Pick disease (NPD) is caused by abnormal storage of sphingomyelin. NPD may affect the pulmonary system and cause hypoxia. In the present case, both hepatopulmonary syndrome (HPS) and pulmonary arteriovenous fistulas (PAVFs) developed in a child with NPD and were successfully treated with repeated embolization. Case Presentation: We have reported the case of a 16-year-old-girl with NPD who suffered severe hypoxia, dyspnea, fatigue, had multiple PAVFs, and was diagnosed with type 2 HPS. To improve oxygenation, 10 PAVFs were embolized. She needed re-embolization after 9 months because of hypoxia redevelopment. Conclusions: Pulmonary involvement, HPS, and/or PAVFs could be responsible for hypoxemia in patients with NPD, who should, therefore, be investigated for HPS and PAVFs. Embolization could be beneficial. Some patients may need repeated embolization.

Clinical relevance of endpoints in clinical trials for acid sphingomyelinase deficiency enzyme replacement therapy

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) also known as Niemann-Pick disease, is a rare lysosomal storage disorder with a diverse disease spectrum that includes slowly progressive, chronic visceral (type B) and neurovisceral forms (intermediate type A/B), in addition to infantile, rapidly progressive fatal neurovisceral disease (type A).

PURPOSE AND METHODS

We review the published evidence on the relevance of splenomegaly and reduced lung diffusion capacity to the clinical burden of chronic forms of ASMD. Targeted literature searches were conducted to identify relevant ASMD and non-ASMD studies for associations between diffusing capacity of the lungs for carbon monoxide (DL_CO) and splenomegaly, with clinical parameters and outcome measures.

RESULTS

Respiratory disease and organomegaly are primary and independent contributors to mortality, disease burden, and morbidity for patients with chronic ASMD. The degree of splenomegaly correlates with short stature, atherogenic lipid profile, and degree of abnormality of hematologic parameters, and thus may be considered a surrogate marker for bleeding risk, abnormal lipid profiles and possibly, liver fibrosis. Progressive lung disease is a prevalent clinical feature of chronic ASMD, contributing to a decreased quality of life (QoL) and an increased disease burden. In addition, respiratory-related complications are a major cause of mortality in ASMD.

CONCLUSIONS

The reviewed evidence from ASMD natural history and observational studies supports the use of lung function and spleen volume as clinically meaningful endpoints in ASMD trials that translate into important measures of disease burden for patients.

Combined Emphysema and Interstitial Lung Disease as a Rare Presentation of Pulmonary Involvement in a Patient with Chronic Visceral Acid Sphingomyelinase Deficiency (Niemann-Pick Disease Type B)

BACKGROUND Niemann-Pick disease is a rare genetic disorder caused by mutations in sphingomyelin phosphodiesterase 1 gene. It results in acid sphingomyelinase deficiency (ASMD) and sphingomyelin intracellular accumulation. Lung disease is diagnosed mostly in chronic visceral ASMD. Ground-glass opacities and smooth interlobular septal thickening are described most frequently. They are localized predominantly in the lower parts of both lungs. CASE REPORT The authors describe a rare type of lung involvement, composed of emphysema and interstitial lung disease (ILD), in a nonsmoking adult male with chronic visceral ASMD. Areas of ground-glass opacities and lung fibrosis presenting as reticulation and bronchiectasis have been described in high-resolution computed tomography of the lungs. The radiological findings were localized predominantly in the middle and lower parts of both lungs. Large air spaces of marginal emphysema, localized in the upper lobes, were also demonstrated. Foamy macrophages, staining blue with May-Grünwald-Giemsa, were found in bronchoalveolar lavage, confirming lung involvement in the course of ASMD. The course of disease was stable, with no hypoxemia at rest. Nevertheless, because of markedly decreased lung transfer for carbon monoxide and significant desaturation on exertion, further controls have been planned, with qualification for long-term oxygen therapy in case of deterioration. CONCLUSIONS We present a unique type of lung involvement, combined emphysema and ILD, in a nonsmoking adult patient with chronic visceral ASMD. On such occasion chronic obstructive pulmonary disease coexisting with ILD as well as chronic pulmonary fibrosis and emphysema syndrome should be excluded.

Homozygous pArg610del Mutation Unusually Associated With Severe Delay of Growth in 2 Acid Sphingomyelinase Deficiency-affected Sibs

BACKGROUND

Typically, patients with Acid Sphingomyelinase Deficiency (ASMD) because of p.Arg610del mutation, have mild phenotype with normal linear growth.

OBSERVATION

We reported the case of 2 Tunisian brothers who have been referred for splenomegaly, polyadenopathies, pubertal, and growth delay. Molecular testing of SMPD1 gene revealed the presence of a homozygous p.Arg610del mutation. Lysosphingomyelin and its isoform-509 were both increased confirming ASMD for both cases. Growth hormone deficiency was highly suspected but growth hormone response after stimulating tests was acceptable for both patients.

CONCLUSIONS

There is no correlation between phenotype-genotype in case of p.Arg610del mutation that could be associated to a severe delay of growth.

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.

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.

Respiratory impairment in Niemann-Pick B disease: Two case reports and review for the pulmonologist

Acid sphingomyelinase deficiency (ASMD), also called Niemann-Pick disease, is a storage disorder with pulmonary involvement but few respiratory symptoms in adults. However, the disease may evolve towards clinically relevant respiratory symptoms with referral to the pulmonologist for management and care. Based on two case reports illustrating respiratory impairment, the aim of this work was to review clinical features, diagnosis, respiratory prognostic and therapeutics for the pulmonologist. Overall, storage disorder should be suspected in the presence of hepatosplenomegaly and interstitial lung disease. Concomitant thrombopenia or hyperlipidemia should also draw attention. Following recent consensus guidelines, diagnosis is based on enzyme assay for ASM activity in blood, with subsequent gene sequencing once the biochemical diagnosis has been confirmed. Disease is slowly progressive and the main causes of death are respiratory and liver failure. Presence of emphysema lesions or worsening of respiratory symptoms should call for the intensification of treatment. Though enzyme replacement therapy is a promising way of development, lung transplantation might be considered for these patients in the absence of contraindication.