TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: MPS6Z    
Mucopolysaccharidosis VI, Full Gene Analysis, Varies

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

Identifying variants within the ARSB gene

 

Confirmation of a diagnosis of mucopolysaccharidosis type VI

 

Carrier testing, when there is a family history of mucopolysaccharidosis type VI, but disease-causing variants have not been previously identified

Genetics Test Information Provides information that may help with selection of the correct genetic test or proper submission of the test request

Testing includes full gene sequencing of the ARSB gene.

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

If a skin biopsy is received, fibroblast culture and cryopreservation for biochemical studies will be performed at an additional charge.

 

See Lysosomal Storage Disorders Diagnostic Algorithm, Part 1 in Special Instructions.

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

Mucopolysaccharidosis type VI (MPS-VI), also known as Maroteaux-Lamy syndrome, is an autosomal recessive condition that is caused by variants in the ARSB gene and is characterized by reduced or absent activity of the arylsulfatase B enzyme. This test screens for variants in all 8 exons of the ARSB gene.

 

The clinical features and severity of symptoms of Maroteaux-Lamy are widely variable. Typically it is characterized by short stature, dysostosis multiplex, facial dysmorphism, stiff joints, hepatosplenomegaly, corneal clouding, cardiac defects, and usually normal intelligence. With a rapidly progressing form of MPS-VI, onset occurs before 2 to 3 years of age with death typically occurring in the second to third decade. With a slowly progressing form of MPS-VI, a diagnosis usually occurs after 5 years of age but may not occur until the second or third decade.

 

The recommended first-tier test for MPS-VI is measurement of mucopolysaccharides in urine (MPSQU / Mucopolysaccharides Quantitative, Random, Urine) or enzyme testing for arylsulfatase B.

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.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

All detected alterations are evaluated according to American College of Medical Genetics and Genomics (ACMG) recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

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

A small percentage of individuals who are carriers or have a diagnosis of mucopolysaccharidosis type VI (MPS-VI) may have a variant that is not identified by this method (eg, large genomic deletions, promoter alterations). The absence of a variant, therefore, does not eliminate the possibility of positive carrier status or the diagnosis of MPS-VI. The preferred approach to carrier testing is to first document the presence of an ARSB gene variant in an affected family member.

 

In some cases, DNA alterations of undetermined significance may be identified.

 

Rare alterations exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.

 

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in the interpretation of results may occur if information given is inaccurate or incomplete.

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

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015 May;17(5):405-424

2. Litjens T, Hopwood JJ: Mucopolysaccharidosis type VI: Structural and clinical implications of mutations in N-acetylgalactosamine-4-sulfatase. Hum Mutat. 2001;18(4):282-295

3. Valayannopoulos V, Nicely H, Harmatz P, Turbeville S: Mucopolysaccharidosis VI. Orphanet J Rare Dis. 2010;5:5

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