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Test ID MPS2Z Hunter Syndrome, Full Gene Analysis

Useful For

Confirmation of a diagnosis of mucopolysaccharidosis type II (Hunter syndrome)

 

Carrier testing when there is a family history of mucopolysaccharidosis type II (Hunter syndrome), but disease-causing mutations have not been previously identified

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
CULFB Fibroblast Culture for Genetic Test Yes No

Testing Algorithm

If skin biopsy is received, fibroblast culture for genetic test will be added and charged separately.

 

The recommended first-tier test for mucopolysaccharidosis type II is biochemical testing that measures iduronate 2-sulfatase enzyme activity in fibroblasts: IDNS / Iduronate Sulfatase, Fibroblasts. Individuals with decreased or absent enzyme activity are more likely to have a mutation in the IDS gene identifiable by this test.

Method Name

Polymerase Chain Reaction (PCR) Amplification/DNA Sequencing
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)

Reporting Name

Hunter Syndrome, Full Gene Analysis

Specimen Type

Varies

Forms:

1. Molecular Genetics: Biochemical Disorders Patient Information (T527) in Special Instructions

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

 

Specimen preferred to arrive within 96 hours of collection.

 

Submit only 1 of the following specimens:

 

Preferred:

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated

 

Specimen Type: Cultured fibroblasts

Container/Tube: T-75 or T-25 flask

Specimen Volume: 1 Full T-75 flask or 2 full T-25 flasks

Specimen Stability Information: Ambient (preferred)/Refrigerated <24 hours

 

Specimen Type: Skin biopsy

Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [Supply T115]).

Specimen Volume: 4-mm punch

Specimen Stability Information: Refrigerated (preferred)/Ambient

 

Specimen Type: Blood spot

Container/Tube:

Preferred: Collection card (Whatman Protein Saver 903 Paper)

Acceptable: Ahlstrom 226 filter paper, or Blood Spot Collection Card (T493)

Specimen Volume: 2 to 5 Blood Spots on collection card (Whatman Protein Saver 903 Paper; Ahlstrom 226 filter paper; or Blood Spot Collection Card, T493)

Collection Instructions:

1. An alternative blood collection option for a patient >1 year of age is finger stick.

2. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry

Specimen Minimum Volume

Blood: 1 mL/Blood Spots: 5 punches, 3-mm diameter

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies

Clinical Information

Mucopolysaccharidosis type II (MPS-II), also known as Hunter syndrome, is a rare X-linked condition caused by mutations in the IDS gene. MPS-II is characterized by reduced or absent activity of the iduronate 2-sulfatase enzyme.

                                                                             

The clinical features and severity of symptoms of MPS-II are widely variable, ranging from severe disease to an attenuated form, which generally presents at a later onset with a milder clinical presentation. In general, symptoms may include coarse facies, short stature, enlarged liver and spleen, joint contractures, cardiac disease, and profound neurologic involvement leading to developmental delays and regression. Female carriers are usually asymptomatic.

 

The IDS gene is located on the X chromosome and has 9 exons. IDS is the only known gene to be associated with MPS-II. The recommended first-tier test for MPS-II is biochemical testing that measures iduronate 2-sulfatase enzyme activity in fibroblasts: IDNS / Iduronate Sulfatase, Fibroblasts. Individuals with decreased or absent enzyme activity are more likely to have a mutation in the IDS gene identifiable by molecular gene testing. However, enzymatic testing is not reliable to detect carriers.

 

This test screens for mutations in all 9 exons of the IDS gene.

Reference Values

An interpretive report will be provided.

Cautions

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

 

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

 

Rare polymorphisms 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.

 

A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.

 

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

Day(s) Performed

Performed weekly, varies

Report Available

14 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81405-IDS (iduronate 2-sulfatase) (eg,mucopolysacchridosis, type II), full gene sequence

 

Fibroblast Culture for Genetic Test

88233-Tissue culture, skin, or solid tissue biopsy (if appropriate)

88240-Cryopreservation (if appropriate)

NY State Approved

Yes