Monitoring effectiveness of treatment in patients with phosphomannomutase 2 deficiency (PMM2-CDG)
Establishing a baseline level prior to initiating treatment for PMM2-CDG
This test is not useful for diagnosing congenital disorders of glycosylation (CDG) in general or PMM2-CDG in particular
Gas Chromatography-Mass Spectrometry (GC-MS)
Polyols
Glucitol
Sugar alcohols
Urine
Patient's age is required.
Supplies: Urine Tubes, 10 mL (T068)
Container/Tube: Plastic, 10-mL urine tube
Specimen Volume: 2 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
1 mL
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Urine | Refrigerated (preferred) | 28 days | |
Frozen | 28 days |
Monitoring effectiveness of treatment in patients with phosphomannomutase 2 deficiency (PMM2-CDG)
Establishing a baseline level prior to initiating treatment for PMM2-CDG
This test is not useful for diagnosing congenital disorders of glycosylation (CDG) in general or PMM2-CDG in particular
In many patients with PMM2-CDG, the urine polyols, sorbitol and mannitol, are elevated relative to controls. Sorbitol, in particular, has been shown to be positively correlated with severely affected patients in contrast to patients in the mild or moderate categories. It is also higher in patients with moderate peripheral neuropathy. Both mannitol and sorbitol were increased in patients with mild liver dysfunction.(1) Treatment options for PMM2-CDG remain limited however; current literature reports that the aldose reductase inhibitor, epalrestat, can correct the underlying enzyme deficiency in a majority of patients with PMM2-CDG.(2) Recent trials suggest that treatment with epalrestat, in addition to other therapeutic benefits, resulted in nearly normalized levels of sorbitol and mannitol relative to controls.(1)
Mannitol: <97 mmol/mol creatinine
Sorbitol: <35 mmol/mol creatinine
The quantitative results of sorbitol and mannitol are reported without added interpretation.
No significant cautionary statements
1. Ligezka AN, Radenkovic S, Saraswat M, et al: Sorbitol is a severity biomarker for PMM2-CDG with therapeutic implications. Ann Neurol. 2021 Dec;90(6):887-900. doi: 10.1002/ana.26245
2. Iyer S, Sam FS, DiPrimio N, et al: Repurposing the aldose reductase inhibitor and diabetic neuropathy drug epalrestat for the congenital disorder of glycosylation PMM2-CDG. Dis Model Mech. 2019 Nov 11;12(11):dmm040584. doi: 10.1242/dmm.040584
A total of 200 mcL of urine is spiked with a mixture of labeled internal standards, allowed to equilibrate, and evaporated. The dry residue is derivatized to form trimethylsilyl esters, then extracted with hexane. Specimens are analyzed by gas chromatography/mass spectrometry, selected ion monitoring using ammonia chemical ionization and a stable isotope dilution method.(Jansen G, Muskiet F, Schierbeek H, et al: Capillary gas chromatography profiling of urinary, plasma, and erythrocyte sugars and polyols as their trimethylsilyl derivatives, preceded by a simple and rapid prepurification method. Clin Chim Acta. 1986 Jun 30; 157[3]:277-294; Marolt G, Kolar M. Analytical methods for determination of phytic acid and other inositol phosphates: A review. Molecules. 2020 Dec 31;26[1]:174)
Tuesday
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 US Food and Drug Administration.
82542
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
SORBU | Sorbitol and Mannitol, QN, U | 74447-4 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
614935 | Sorbitol | 48152-3 |
614936 | Mannitol | 47698-6 |
614937 | Interpretation | 59462-2 |
614938 | Reviewed By | 18771-6 |
Change Type | Effective Date |
---|---|
New Test | 2022-06-16 |