Antigenic determinants in IgM parapotein-related neuropathies

The association of neuropathy with IgM paraprotein has been known for several years, but only recently the pathogenetic relevance of this association has been clarified. Reactivity of the paraprotein with several neural antigens has been reported even if their pathogenetic relevance is not always clear. IgM binding to the Myelin-associated glycoprotein (MAG) is associated with a homogeneous demyelinating neuropathy, deposits of the paraprotein and complement on nerve myelin, and improvement concomitantly to anti-MAG IgM reduction. In particular, treatment with rituximab durably improved the neuropathy in two thirds of the patients, particularly those with moderately increased anti-MAG titres, which might be more easily reduced by this treatment. Several other IgM reactivities with nerve antigens have been reported in these patients, including several gangliosides and sulfatide even if, with the only exceptions of anti-sulfatide and anti-GQ1b ganglioside reactivities, their possible pathogenetic relevance remains to be established.