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Test Catalog

Test ID: OXNP    
Oxysterols, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Investigation of possible diagnoses of Niemann-Pick disease types A, B, or C in plasma specimens

 

Monitoring of individuals with Niemann-Pick type C disease

 

This test is not useful for the identification of carriers.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Niemann-Pick disease types A, B, and C (NPA, NPB, and NPC, respectively) are a group of autosomal recessive lysosomal storage disorders affecting metabolism of specific lipids within cells.

 

NPA and NPB are caused by a deficiency of sphingomyelinase that results in extensive storage of sphingomyelin and cholesterol in the liver, spleen, lungs, and, to a lesser degree, brain. NPA disease is more severe than NPB and is characterized by early onset with feeding problems, dystrophy, persistent jaundice, development of hepatosplenomegaly, neurological deterioration, deafness, and blindness leading to death by age 3 years. NPB disease is limited to visceral symptoms with survival into adulthood. Some patients have been described with intermediary phenotypes. Characteristic of the disease are large lipid-laden foam cells. Approximately 50% of cases have cherry-red spots in the macula. Sphingomyelinase is encoded by the SMPD1 gene.

 

The combined prevalence of NPA and NPB is estimated to be 1 in 250,000. NPA and NPB are inherited in an autosomal recessive manner and are caused by variants in the SMPD1 gene. Although there is a higher frequency of type A among the Ashkenazi Jewish population, both types are panethnic. Individuals with NPA and NPB typically have elevations of lyso-sphingomyelin (LSM) and lyso-sphingomyelin 509 (LSM 509) combined with potential elevations in cholestane-3 beta, 5 alpha, 6 beta-triol or 7-ketocholesterol (7-KC). Molecular genetic testing for NPA and NPB disease is also available (see NPABZ / Niemann-Pick Disease, Types A and B, Full Gene Analysis, Varies).

 

NPC is caused by a defect in cellular cholesterol trafficking that results in the progressive accumulation of unesterified cholesterol in late endosomes/lysosomes.(1) NPC is considered a lipid storage disorder with variable age of onset (range: perinatal period to adulthood), and highly variable clinical presentation. Most individuals are diagnosed during childhood with symptoms that include ataxia, vertical supranuclear gaze palsy, dystonia, progressive speech deterioration, and seizures. Infants may present with or without hepatosplenomegaly and respiratory failure. Those without liver and pulmonary disease may present with hypotonia and developmental delay. Adult-onset NPC is associated with a slower progression and is characterized by psychiatric illness, ataxia, dystonia, and speech difficulties.

 

The incidence of NPC is approximately 1 in 120,000 to 150,000 live births. NPC is an autosomal recessive condition and is caused by variants in either the NPC1 or NPC2 genes. Individuals with NPC exhibit elevated levels of oxysterol cholestane-3 beta,5 alpha,6 beta-triol (COT); lyso-sphingomyelin 509 (LSM 509) and 7-ketocholesterol (7-KC) may also be elevated. The diagnosis of NPC can be confirmed by demonstration of impaired cholesterol esterification and positive filipin staining in cultured fibroblasts (NIEM / Niemann-Pick Type C Detection, Fibroblasts). For molecular confirmation, genetic testing for NPC disease can be performed (see NPCZ / Niemann-Pick Type C Disease, Full Gene Analysis, Varies).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

CHOLESTANE-3-BETA, 5-ALPHA, 6-BETA-TRIOL

Cutoff: < or =0.070 nmol/mL

 

7-KETOCHOLESTEROL

Cutoff: < or =0.100 nmol/mL

 

LYSO SPHINGOMYELIN

Cutoff :< or = 0.100 nmol/mL

Interpretation Provides information to assist in interpretation of the test results

An elevation of cholestane-3-beta, 5-alpha, 6-beta-triol (COT) is highly suggestive of Niemann-Pick disease type C (NPC).

 

An elevation of lyso-sphingomyelin (LSM) is highly suggestive of Niemann-Pick type A or B (NPA or NPB) disease.

 

An elevation of lyso-sphingomyelin 509 (LSM 509) is suggestive of NPA, NPB, or NPC disease.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Nonspecific neonatal cholestasis may result in elevations of cholestane-3-beta, 5-alpha, 6-beta-triol (COT) and lyso-sphingomyelin 509 (LSM 509).

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. OMIM: 257220 Niemann-Pick Disease, Type C1; NPC1.. Updated May 26, 2020. Accessed February 3, 2021. Available at www.omim.org/entry/257220?search=257220&highlight=257220

2. OMIM: 257200 Niemann-Pick Disease Type A. Updated October 19, 2016. Accessed February 3, 2021. Available at www.omim.org/entry/257200?search=257200&highlight=257200

3. OMIM: 607616 Niemann-Pick Disease Type B. Updated April 4, 2019. Accessed February 3, 2021. Available at www.omim.org/entry/607616?search=607616&highlight=607616

4. Wasserstein MP, Schuchman EH: Acid sphingomyelinase deficiency. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2006. Updated June 18, 2015. Accessed November 2, 2020. Available at www.ncbi.nlm.nih.gov/books/NBK1370/

5. Patterson MC, Vanier MT, Suzuki K, et al: Niemann-Pick disease type C: a lipid trafficking disorder. In: Valle D, Beaudet AL, Vogelstein B, et al, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed November 2, 2020 Available at ommbid.mhmedical.com/content.aspx?sectionid=225545907&bookid=2709

6. Gal AE, Brady RO, Hibbert SR, Pentchev PG: A practical chromogenic procedure for the detection of homozygotes and heterozygous carriers of Niemann-Pick disease. N Engl J Med. 1975;293:632-636

7. Patterson M: Niemann-Pick disease type C. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated December 10, 2020. Accessed February 3, 2021. Available at www.ncbi.nlm.nih.gov/books/NBK1296/

8. Schuchman EH: The pathogenesis and treatment of acid sphingomyelinase-deficient Niemann-Pick disease. Int J Clin Pharmacol Ther. 2009;47(Suppl 1):S48-S57

9. Hollack CE, de Sonnaville ES, Cassiman D et al: Acid sphingomyelinase (Asm) deficiency patients in The Netherlands and Belgium: disease spectrum and natural course in attenuated patients. Mol Genet Metab. 2012;107:526-533.

10. Geberhiwot T, Moro A, Dardis A, et al: International Niemann-Pick Disease Registry (INPDR). Consensus clinical management guidelines for Niemann-Pick disease type C. Orphanet J Rare Dis. 2018 Apr 6;13(1):50

Special Instructions Library of PDFs including pertinent information and forms related to the test