Light chain deposition in peripheral nerve as a cause of mononeuritis multiplex in Waldenström's macroglobulinaemia.

Waldenström's macroglobulinaemia is a form of monoclonal IgM gammopathy associated with a rare B-cell lympho-plasmacytic lymphoma, characterized by the involvement of bone marrow, lymph nodes and spleen. Neurological complications involving peripheral nerves are common and different pathogenic mechanisms have been reported. We describe a patient with severe multineuropathy associated with Waldenström's macroglobulinaemia. Nerve biopsy revealed copious light chain deposition which subverted the normal architecture of the endoneurium and epineurium resulting in massive fascicular hyalinosis and epineural arteries disruption, respectively. This report confirms that massive immunoglobulin deposition is one of the several mechanisms of nerve damage in IgM-related neuropathy. Since their recognition has important therapeutical consequences, nerve biopsy is an essential diagnostic tool in patients with an unusual clinical presentation of IgM-related neuropathies.