Non-eIF2B-related cystic leukoencephalopathy of unknown origin

Leukodystrophies

Leukodystrophies comprise a broad group of progressive, inherited disorders affecting mainly myelin. They often present after a variable period of normalcy with a variety of neurologic problems. Though the ultimate diagnosis is not found in many patients with leukodystrophies, distinctive features unique to them aid in diagnosis, treatment and prognostication. The clinical characteristics, etiologies, diagnostic testing and treatment options are reviewed in detail for some of the major leukodystrophies: X-linked adrenoleukodystrophy, Krabbe disease, metachromatic leukodystrophy, Pelizaeus-Merzbacher disease, Alexander disease, Canavan disease, megalencephalic leukoencephalopathy with subcortical cysts and vanishing white matter disease.

Sensitivity and specificity of decreased CSF asialotransferrin for eIF2B-related disorder

OBJECTIVE

This is a study estimating diagnostic accuracy of CSF asialotransferrin to transferrin ratio measurement in eIF2B related disorders by using clinical evaluation and EIF2B mutation analysis as the reference standard. eIF2B-related disorder is a relatively common leukodystrophy with broad phenotypic variation that is caused by mutations in any of the five EIF2B genes. There is a need for a simple and clinically valid screening tool for physicians evaluating patients with an unclassified leukodystrophy.

METHODS

CSF two-dimensional gel (2DG) electrophoresis analyses to measure asialotransferrin to transferrin ratios were performed in 60 subjects including 6 patients with documented EIF2B gene mutations, patients with other types of leukodystrophy, and patients with no leukodystrophy.

RESULTS

All six patients with mutation proven eIF2B-related disease showed low to nearly undetectable amounts of asialotransferrin in their CSF when compared to 54 unaffected controls by CSF 2DG analyses in this study. eIF2B-like patients, with clinically similar presentations but no mutations in EIF2B1-5, were distinguished from patients with mutations in EIF2B1-5 by this biomarker. Patients with mutations in EIF2B1-5 had asialotransferrin/transferrin ratio levels significantly different from the group as a whole (p < 0.001). Using 8% asialotransferrin/transferrin ratio as a cutoff, this biomarker has a 100% sensitivity (95% CI = 52-100%) and 94% specificity (95% CI = 84-99%).

CONCLUSION

Decreased asialotransferrin/transferrin ratio in the CSF of patients with eIF2B-related disorder is highly sensitive and specific. This rapid (<48 hours) and inexpensive diagnostic tool for eIF2B-related disorders has the potential to identify patients with likely eIF2B-related disorder for mutation analysis.