[Acid sphingomyelinase deficiency (Niemann-Pick disease type B) in adulthood: A retrospective multicentric study of 28 adult cases]. / Déficit en sphingomyélinase acide (maladie de Niemann-Pick B) : une étude rétrospective multicentrique de 28 patients adultes.

INTRODUCTION: Acid sphingomyelinase deficiency (ASMD) is an autosomal recessive disease with a clinical spectrum ranging from a neurovisceral infantile form (Niemann-Pick disease type A) to a chronic visceral form also encountered in adults (Niemann-Pick disease type B, NP-B). METHODS: Retrospective multicentric analysis of French adult patients with ASMD over the period 1985-March 2015. Clinical, biological, and imaging data were analyzed. RESULTS: Twenty-eight patients (19 males, 9 females) were analyzed. Diagnosis was made before the age of 10 years in 16 cases. Main symptoms at diagnosis were spleen/liver enlargement and interstitial lung disease. Biological abnormalities included: thrombocytopenia (platelet count <150 000/mm3) in 24 cases including 4 patients with platelet count <60 000/mm3, constantly low high-density lipoprotein (HDL) cholesterol, polyclonal hypergammaglobulinemia (n=6), monoclonal gammopathy of unknown significance (n=5), normal prothrombin level discordant with low factor V (n=5), elevated chitotriosidase level (n=11). The diagnosis was confirmed in all cases by deficient acid sphingomyelinase enzyme activity. SMPD1 gene sequencing was performed in 25 cases. The frequent p.R610del mutation was largely predominant, constituting 62% of the non-related alleles. During the follow-up period, three patients died before 50 years of age from cirrhosis, heart failure and lung insufficiency, respectively. CONCLUSION: ASMD in adulthood (NP-B) associates spleen/liver enlargement and interstitial lung disease. Early diagnosis and appropriate management are essential for reducing the risk of complications, improving quality of life, and avoiding inappropriate procedures such as splenectomy. To date, only symptomatic therapy is available. A phase 2/3 therapeutic trial with IV infusion of recombinant enzyme is on-going.

Epidemiological, clinical and biochemical characterization of the p.(Ala359Asp) SMPD1 variant causing Niemann-Pick disease type B.

Niemann-Pick disease type B (NPDB) is a rare, inherited lysosomal storage disorder that occurs due to variants in the sphingomyelin phosphodiesterase 1 (SMPD1) gene and the resultant deficiency of acid sphingomyelinase (ASM) activity. While numerous variants causing NPDB have been described, only a small number have been studied in any detail. Herein, we describe the frequency of the p.(Ala359Asp) variant in the healthy Chilean population, and determine the haplotype background of homozygous patients to establish if this variant originated from a common founder. Genomic DNA samples from 1691 healthy individuals were analyzed for the p.(Ala359Asp) variant. The frequency of p.(Ala359Asp) was found to be 1/105.7, predicting a disease incidence of 1/44 960 in Chile, higher than the incidence estimated by the number of confirmed NPDB cases. We also describe the clinical characteristics of 13 patients homozygous for p.(Ala359Asp) and all of them had moderate to severe NPDB disease. In addition, a conserved haplotype and shared 280 Kb region around the SMPD1 gene was observed in the patients analyzed, indicating that the variant originated from a common ancestor. The haplotype frequency and mitochondrial DNA analysis suggest an Amerindian origin for the variant. To assess the effect of the p.(Ala359Asp) variant, we transfected cells with the ASM-p.(Ala359Asp) cDNA and the activity was only 4.2% compared with the wild-type cDNA, definitively demonstrating the causative effect of the variant on ASM function. Information on common variants such as p.(Ala359Asp) is essential to guide the successful implementation for future therapies and benefit to patients.

Morbidity and mortality in type B Niemann-Pick disease.

PURPOSE: The purpose of this study was to perform a systematic evaluation of morbidity and mortality in type B Niemann-Pick disease. METHODS: A total of 103 patients with Niemann-Pick disease (49 males, 54 females, age range: 1-72 years) participated in natural history studies through Mount Sinai's International Center for Types A and B Niemann-Pick Disease between 1992 and 2012. RESULTS: Serious morbidities included significant neurological, hepatic, and cardiac disease. Thirteen patients had some degree of neurological impairment. Nine patients had cirrhosis or liver failure requiring transplantation. Coronary artery and valvular heart disease were present in nine patients. Of note, only four patients were oxygen dependent, although progressive pulmonary disease is a well-described feature of Niemann-Pick disease. During the follow-up period, 18 deaths occurred. The median age of death was 15.5 years (range 1-72). Causes of death included pneumonia, liver failure, and hemorrhage. The majority of deaths (12 of 18) occurred in patients <21 years, yielding a mortality rate of 19% in the pediatric population. CONCLUSION: This study demonstrates that Niemann-Pick disease is a life-threatening disorder with significant morbidity and mortality, especially in the pediatric population. The information collected in this series highlights the need for safe, effective therapy for Niemann-Pick disease.

Adult-onset pulmonary involvement in Niemann-Pick disease type B.

Niemann-Pick disease type B is caused by a deficiency in acid sphingomyelinase activity; among the six variants of Niemann-Pick disease known to date, it is the most frequently associated with lung involvement, a major cause of morbidity and mortality in this subtype in patients of all ages. Nevertheless, the vast majority of reports in the literature concern infantile forms, while less reported is, for several reasons, the onset in adults being consequently still poorly understood and characterized its clinical, radiographic and functional manifestations. We report a case of a 37 years-old female patient affected by subtype B since she was an infant, operated for aortic valve replacement two years before and came to our attention for the onset of a worsening exertional dyspnoea which proved, through a series of functional tests and radiological exams, to be a consequence of the diffuse lung involvement by the metabolic disorder; we performed a review on this topic through a Medline search of all the available "adult-onset" case reports published since the first description in 1964, also considering the possible association between NPDB and, more generally lysosomal storage disorders, and the valvular disease, already suggested by several Authors in previous works.

Identification and characterization of SMPD1 mutations causing Niemann-Pick types A and B in Spanish patients.

Niemann-Pick disease (NPD) types A/B are both caused by a deficiency of lysosomal acid sphingomyelinase and display autosomal recessive inheritance. These two types of the disease were described according to the presence (type A) or absence (type B) of neurological symptoms. We present a molecular analysis of 19 Spanish NPD A/B patients and two from Maghreb. Eight of the patients had type A and 13 had type B NPD. All mutant SMPD1 alleles were identified, including 17 different mutations, 10 of which were novel. The only frequent mutations in the 21 NPD patients were c.1823_1825delGCC (p.R608del) (38%) and c.1445C>A (p.A482E) (9%). Genotype-phenotype correlations were established for most of the mutations and, in particular, the p.R608del-type B association was confirmed. This mutation accounts for 61.5% of the mutant alleles in the type B subgroup of patients. Expression studies performed on six of the identified mutations confirmed them to be disease-causing due to their low enzyme activity. An allele with a mutation affecting a noncanonical donor splice site produced only aberrant mRNAs, corresponding to previously reported nonfunctional SMPD1 minor transcripts. This study is the first exhaustive mutational analysis of Spanish Niemann-Pick A/B disease patients.