A case of anti-myelin-associated glycoprotein polyneuropathy and multiple sclerosis: one disease instead of two?

A male patient diagnosed elsewhere as having multiple sclerosis (MS) was recently referred to our MS centre. Despite the presence of scattered T2-hyperintense MS-like lesions on MRI and cerebrospinal fluid (CSF) oligoclonal bands, his MS diagnosis was unpersuasive. Distal symmetric hypotonia, tendon areflexia and distal muscle weakness were present. A mostly demyelinating sensory polyneuropathy was disclosed at electroneurography. Serum IgM band, free monoclonal light chains and increased anti-myelin-associated glycoprotein IgM were detected. At 18 months later, and after three intravenous Ig treatments, a clinical electroneurographic improvement was evident along with the disappearance of some brain MRI lesions, reduction of serum anti-myelin-associated glycoprotein (MAG) IgM level and of the number of CSF oligoclonal bands. Although the cause/effect relation cannot be proven, we hypothesise that not only peripheral but also central demyelination may be related to the presence of anti-MAG antibodies with central nervous system (CNS) patterns on MRI resembling those seen in MS.