Phosphomannomutase and Phosphomannose Isomerase, Leukocytes
Use
This test is used for diagnosing congenital disorders of glycosylation Ia (phosphomannomutase-2 deficiency: PMM2-CDG) and Ib (phosphomannose isomerase deficiency: MPI-CDG) as measured in leukocytes. It serves as a follow-up testing for patients with an abnormal type I CDG transferrin isoform profile. These disorders are a subset of inherited metabolic disorders that impact glycan metabolism, often presenting during infancy or childhood with various symptoms ranging from developmental delays to gastrointestinal issues. Early diagnosis is critical for management and potential intervention strategies.
Special Instructions
The test is not useful for carrier testing. For optimal isolation of leukocytes, specimens should arrive refrigerated within 6 days of collection. It is recommended to collect specimens Monday through Thursday and avoid collecting the day before a holiday. Ensure the specimen is collected and packaged as close to shipping time as possible. For New York clients, informed consent is required.
Limitations
This test does not support carrier testing for phosphomannomutase-2 deficiency (PMM2) or phosphomannose isomerase deficiency (MPI). There are some known carriers of PMM2 deficiency who have reduced enzyme activity within the range of affected patients, which may lead to diagnostic confusion. However, white blood cell enzyme activity remains more reliable than fibroblast testing for PMM2-CDG.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 100735-0
- 78970-1
- 78963-6
- 42349-1
- 31208-2
- 57723-9
- 82785-7
- 85069-3
- 48767-8
- 82772-5
- 59462-2
- 18771-6
Result Turnaround Time
30-45 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
6 mL
Minimum Volume
3 mL
Container
Yellow top (ACD solution B preferred, ACD solution A acceptable)
Collection Instructions
Send specimen in original tube. Do not aliquot. Collect specimen Monday through Thursday only and avoid holidays.
Storage Instructions
Refrigerate within 6 days of collection
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 6 days |
| Refrigerated | 6 days |