Marked elevation of urinary β2-microglobulin in patients with reversible splenial lesions: A small case series

Highlight
• We report four patients with reversible splenial lesions.
• All four cases showed markedly increased urinary β2-microglobulin (β2MG) levels.
• Elevated urinary β2MG may reflect an excessive immune response.
• Excessive immune response might play a role in the pathogenesis of reversible splenial lesions.

The magnetic resonance imaging findings of reversible isolated lesions with transiently reduced diffusion in the splenium of corpus callosum of patients with a wide spectrum of pathological conditions are referred to as reversible splenial lesion syndrome (RESLES). Clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is probably included within the spectrum of RESLES; however, its exact pathophysiology is not known. Here, we describe three patients with MERS and one patient with RESLES, all of whom showed elevated urinary β2-microglobulin regardless of diagnosis and presence of pathogens. Elevated urinary β2-microglobulin suggested that an excessive immune response might play a role in the pathophysiology of reversible splenial lesions.