Cerebral White Matter Demyelination in Vitamin B12 Deficiency: A Case Report

Abstract

Vitamin B12 deficiency has been classically associated with subacute combined degeneration of the cord. It can be readily recognized on magnetic resonance imaging as T2W hyperintensity of the dorsal column. Cerebral changes are being increasingly notified, especially in the elderly population. The authors report the case of a 33-year-old patient and describe the imaging characteristics.

Vitamin B12 Deficiency and the Nervous System: Beyond Metabolic Decompensation—Comparing Biological Models and Gaining New Insights into Molecular and Cellular Mechanisms

“…It is comprised of two essential components: cubilin (CUB), encoded by the CUBN gene, and amnionless (AMN), encoded by AMN. However, additional proteins may contribute to the stability and function of this complex, including megalin (MAG), encoded by the LRP-2 gene, and receptor-associated protein (RAP), which interacts with specific components of the cubam complex [ 20 , 21 ]. Once the VitB12-IF complex reaches the lysosomes, IF undergoes degradation, releasing free VitB12, which is then actively transported into the cytoplasm with the help of two transmembrane proteins encoded by the LMBRD1 and ABCD4 genes [ 22 ].…”

“…Following receptor-mediated endocytosis, within the lysosome, TC is degraded, and the CD320 receptor is recycled to the plasma membrane. In this manner, VitB12, no longer complexed to a protein, can enter the cytoplasm via lysosomal transporters for utilization by specific enzymes (MTR and MUT) and may even be exported [ 20 , 21 ].…”

“…These mechanisms contribute to the aggravation of EAE symptoms in VitB12-restricted animals, shedding light on the involvement of this vitamin in neuroinflammatory conditions generally associated with MS [ 63 ]. Remarkably, in humans, clinical findings and MRI images often exhibit similar results for VitB12 deficiency and MS, including cerebral white matter demyelination, posing a significant challenge in accurately distinguishing between the two very different diagnoses [ 21 ]. Also, within MS patients, a reduction in VitB12 levels has been observed [ 139 ]; however, at the clinical level, it is known that VitB12 is crucial for the initial myelination and development of the CNS, as well as sustain its regular functioning.…”

“…At the biochemical level, it is conceivable that the deficiency of SAM hampers the methylation of basic myelin protein and lipids, which can be detrimental to the myelin sheath. Furthermore, the build-up of methylmalonyl-CoA can result in a decline in normal myelin synthesis and the incorporation of anomalous fatty acids into neuronal lipids [ 21 , 141 ]. VitB12 deficiency can also influence myelin homeostasis by modifying the activity of oligodendrocytes and modulating the inflammation resulting in axon demyelination, thereby resulting in neuron injury and degeneration [ 139 , 142 ].…”