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HelpTest Code GNMY9 MYH9-Related Disorders, MYH9 Gene, Next-Generation Sequencing, Varies
Ordering Guidance
This test is designed to evaluate MYH9-related disorders, including May-Hegglin disorder/anomaly and Sebastian syndrome, and to be utilized for genetic confirmation of a phenotypic diagnosis of an MYH9-related disorder.
If testing for hereditary platelet disorders using a larger panel is desired, a 70-gene platelet disorder panel is available; order GNPLT / Platelet Disorders, Comprehensive Gene Panel, Next-Generation Sequencing, Varies.
This test is not designed to evaluate for hereditary bleeding disorders. For patients with clinical suspicion of an inherited bleeding disorder, it is important to exclude plasmatic factor deficiencies (eg, von Willebrand disease, hemophilia, or other factor deficiencies) prior to considering an inherited platelet function defect. If bleeding is the indication for testing and testing for hereditary bleeding disorders is desired, bleeding panels are available. For more information see GNBLF / Bleeding Disorders, Focused Gene Panel, Next-Generation Sequencing, Varies or GNBLC / Bleeding Disorders, Comprehensive Gene Panel, Next-Generation Sequencing, Varies.
For assessment of hereditary platelet disorders that have ultrastructural abnormalities, such as gray platelet syndrome, order PTEM / Platelet Transmission Electron Microscopic Study, Whole Blood.
For assessment of hereditary platelet disorders due to quantitative surface glycoprotein deficiencies, order PLAFL / Platelet Glycoprotein Flow Platelet Surface Glycoprotein by Flow Cytometry, Blood.
Testing for the MYH9 gene as part of a customized panel is available. For more information see CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies.
Targeted testing for familial variants (also called site-specific or known variants testing) is available for the MYH9 gene. See FMTT / Familial Variant, Targeted Testing, Varies. To obtain more information about this testing option, call 800-533-1710.
Shipping Instructions
Specimen preferred to arrive within 96 hours of collection.
Necessary Information
Platelet Esoteric Testing Patient Information is required. Testing may proceed without the patient information, however, the information aids in providing a more thorough interpretation. Ordering providers are strongly encouraged to fill out the form and send with the specimen.
Specimen Required
Specimen Type: Whole blood
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.
Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Yellow top (ACD)
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated
Forms
1. Platelet Esoteric Testing Patient Information is required.
2. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing (Spanish) (T826)
3. If not ordering electronically, complete, print, and send an Coagulation Test Request (T753) with the specimen.
Secondary ID
619299Useful For
Evaluating MYH9-related disorders, including May-Hegglin disorder/anomaly and Sebastian syndrome, in patients with a personal or family history suggestive of an MYH9-related disorder
Diagnosing MYH9-related disorders, including May-Hegglin disorder/anomaly and Sebastian syndrome, for patients in whom phenotypic testing is nondiagnostic, but there is a strong clinical suspicion of the MYH9-related disorder
Confirming an MYH9-related disorder diagnosis with the identification of a known or suspected disease-causing alteration in the MYH9 gene
Determining the disease-causing alterations within the MYH9 gene to delineate the underlying molecular defect in a patient with a laboratory diagnosis of an MYH9-related disorder
Identifying the causative alteration for genetic counseling purposes
Prognosis and risk assessment based on the genotype-phenotype correlations
Providing a prognosis in syndromic MYH9-related disorders
Carrier testing for close family members of an individual with an MYH9-related disorder diagnosis
This test is not intended for prenatal diagnosis
Testing Algorithm
The clinical workup for detecting inherited platelet disorders should begin with a careful review of a patient’s complete blood cell count and platelet indices results, peripheral blood smear, and other platelet tests, such as light transmission platelet aggregometry, electrical impedance whole blood aggregometry, and platelet function analyzer 100 (PFA-100). Platelet transmission electron microscopy is an essential tool for laboratory diagnosis of various hereditary platelet disorders, and platelet flow cytometric analysis is the preferred method to assess hereditary platelet disorders due to quantitative surface glycoprotein deficiencies
Due to the reduced sensitivity of functional testing, occasionally, the clinical picture may be consistent with a defect in primary hemostasis, but results of platelet tests may be normal or non-diagnostic.
Genetic testing for hereditary platelet disorders is indicated if:
-Platelet tests indicate a deficiency or functional abnormality, and abnormal platelet or white blood cell morphology by light or electron microscopy
-There is a clinical suspicion for a hereditary platelet disorder due to family history or patient’s clinical presentation
-Acquired causes of deficiencies associated with platelet disorders have been excluded
If a platelet disorder is a concern, a set of clinical guidelines from the British Society for Haematology on testing for heritable platelet disorders is freely available.(1)
Special Instructions
Method Name
Sequence Capture and Targeted Next-Generation Sequencing (NGS) followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing.
Specimen Type
VariesSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Varies | ||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
An interpretive report will be provided.
Interpretation
All detected variants are evaluated according to American College of Medical Genetics and Genomics recommendations.(8) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.
Method Description
Next-generation sequencing (NGS) and/or Sanger sequencing are performed to test for the presence of variants in coding regions and intron/exon boundaries of the MYH9 gene, as well as some other regions that have known disease-causing variants. The human genome reference GRCh37/hg19 build was used for sequence read alignment. At least 99% of the bases are covered at a read depth over 30X. Sensitivity is estimated at above 99% for single nucleotide variants, above 94% for deletion-insertions less than 40 base pairs (bp), above 95% for deletions up to 75 bp and insertions up to 47 bp. NGS and/or a polymerase chain reaction-based quantitative method is performed to test for the presence of deletions and duplications in the MYH9 gene.
There may be regions of the MYH9 gene that cannot be effectively evaluated by sequencing or deletion and duplication analysis as a result of technical limitations of the assay, including regions of homology, high guanine-cytosine (GC) content, and repetitive sequences.(Unpublished Mayo method)
The reference transcript for MYH9 is NM_002473.5. Reference transcript numbers may be updated due to transcript re-versioning. Always refer to the final patient report for gene transcript information referenced at the time of testing. Confirmation of select reportable variants may be performed by alternate methodologies based on internal laboratory criteria.
Day(s) Performed
Varies
Report Available
28 to 42 daysSpecimen Retention Time
Whole blood: 2 weeks (if available); Extracted DNA: 3 monthsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
81479
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| GNMY9 | MYH9 Gene, Full Gene NGS | 105332-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 619300 | Test Description | 62364-5 |
| 619301 | Specimen | 31208-2 |
| 619302 | Source | 31208-2 |
| 619303 | Result Summary | 50397-9 |
| 619304 | Result | 82939-0 |
| 619305 | Interpretation | 69047-9 |
| 619306 | Additional Results | 82939-0 |
| 619307 | Resources | 99622-3 |
| 619308 | Additional Information | 48767-8 |
| 619309 | Method | 85069-3 |
| 619310 | Genes Analyzed | 82939-0 |
| 619311 | Disclaimer | 62364-5 |
| 619312 | Released By | 18771-6 |