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HelpTest Code PMMIL Phosphomannomutase and Phosphomannose Isomerase, Leukocytes
Reporting Name
PMM-PMI, LeukocytesUseful For
Diagnosing congenital disorders of glycosylation Ia (phosphomannomutase-2 deficiency: PMM2-CDG) and Ib (phosphomannose isomerase deficiency: MPI-CDG) as measured in leukocytes
Follow-up testing for patients with an abnormal type I CDG transferrin isoform profile
This test is not useful for carrier testing.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Whole Blood ACDOrdering Guidance
The initial screening test for congenital disorders of glycosylation is transferrin isoform analysis (CDG / Carbohydrate Deficient Transferrin for Congenital Disorders of Glycosylation, Serum). The results of the transferrin isoform analysis should be correlated with the clinical presentation to determine the most appropriate testing strategy, which may include this test.
Shipping Instructions
For optimal isolation of leukocytes, it is recommended the specimen arrive refrigerated within 6 days of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.
Specimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A)
Specimen Volume: 6 mL
Collection Instructions: Send specimen in original tube. Do not aliquot.
Specimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood ACD | Refrigerated (preferred) | 6 days | YELLOW TOP/ACD |
| Ambient | 6 days | YELLOW TOP/ACD |
Special Instructions
Reference Values
PHOSPHOMANNOMUTASE
Normal >350 nmol/h/mg protein
PHOSPHOMANNOSE ISOMERASE
Normal >1,300 nmol/h/mg protein
Day(s) Performed
Preanalytical processing: Monday through Saturday
Assay performed: Twice per month
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82657
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PMMIL | PMM-PMI, Leukocytes | 100735-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 50836 | Specimen | 31208-2 |
| 50837 | Specimen ID | 57723-9 |
| 50838 | Source | 31208-2 |
| 50839 | Order Date | 82785-7 |
| 50840 | Reason For Referral | 42349-1 |
| 50841 | Method | 85069-3 |
| 50842 | Phosphomannomutase, Leuko | 78970-1 |
| 50843 | Phosphomannose Isomerase, Leuko | 78963-6 |
| 50844 | Interpretation | 59462-2 |
| 50845 | Amendment | 48767-8 |
| 50846 | Reviewed By | 18771-6 |
| 50847 | Release Date | 82772-5 |
Interpretation
Normal results are not consistent with either phosphomannomutase-2 deficiency (PMM2-CDG) or phosphomannose isomerase deficiency (MPI-CDG).
Markedly reduced activity of phosphomannomutase is consistent with a diagnosis of PMM2-CDG. Markedly reduced activity of phosphomannose isomerase is consistent with a diagnosis of MPI-CDG.
Mild to moderately reduced enzyme activities will be interpreted in the context of clinical and other laboratory test information submitted with the specimen.
Clinical Reference
1. Grunewald S, Schollen E, Van Schaftingen E, Jaeken J, Matthijs G. High residual activity of PMM2 in patients' fibroblasts: possible pitfall in the diagnosis of CDG-Ia (phosphomannomutase deficiency). Am J Hum Genet. 2001;68(2):347-354
2. Pirard M, Matthijs G, Heykants L, et al. Effect of mutations found in carbohydrate-deficient glycoprotein syndrome type IA on the activity of phosphomannomutase 2. FEBS Lett. 1999;452(3):319-322
3. Lam C, Krasnewich DM. PMM2-CDG. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2005. Updated May 20, 2021. Accessed January 19, 2024. Available at: www.ncbi.nlm.nih.gov/books/NBK1110/
4. Schiff M, Roda C, Monin ML, et al. Clinical, laboratory and molecular findings and long-term follow-up data in 96 French patients with PMM2-CDG (phosphomannomutase 2-congenital disorder of glycosylation) and review of the literature. J Med Genet. 2017;54(12):843-851
5. Girard M, Douillard C, Debray D, et al. Long term outcome of MPI-CDG patients on D-mannose therapy. J Inherit Metab Dis. 2020;43(6):1360-1369
6. Jaeken J, Matthijs G, Carchon H, Van Schaftingen E. Defects of N-glycan synthesis. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed January 19, 2024. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225081470
Report Available
30 to 45 daysMethod Name
Colorimetric
Forms
1. 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 in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Biochemical Genetics Patient Information (T602) in Special Instructions
3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Testing Algorithm
For more information see Congenital Disorders of Glycosylation: Screening Algorithm.