SY7.5. Diagnosis and treatment of paraproteinemic neuropathies

Abstract

There are several neuropathies associated with paraproteinemia: AL-amyloidosis, anti-myelin associated glycoprotein (MAG) neuropathy, and POEMS syndrome. They can be sometimes diagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP), but their therapeutic strategies are clearly different from those for CIDP. Appropriate diagnosis and early treatment are essential to improve prognosis of paraproteinemic neuropathies. AL-amyloidosis is a systemic and fatal disorder associated with plasma cell dyscrasia. Its neuropathy is characterized by length-dependent axonal polyneuropathy and autonomic neuropathy. Because diffuse mild conduction slowing and/or prolonged distal latency in the median nerve, which is caused by deposition of amyloid in the carpal tunnel, are sometimes found, AL-amyloidosis can be initially diagnosed as CIDP. Therapeutic approach to myeloma with autologous stem-cell transplantation or proteasome inhibitors can be effective. AL- amyloidosis usually deteriorates subacutely and delay in starting treatment can progress to fatal outcome. Similar to AL-amyloidosis, POEMS syndrome is a systemic and fatal disorder based on monoclonal plasma cell proliferation. POEMS neuropathy can be summarized as diffusely distributed demyelinating polyneuropathy and it can be frequently diagnosed as CIDP. It is not usually associated with dysautonomia. Disease progression leads to multiple organ failure and long-lasting neurological sequelae. Early therapeutic intervention is a key to improve its prognosis. As with AL-amyloidosis, treatments for myeloma can be used for POEMS syndrome. The efficacy of autologous stem-cell transplantation, immunomodulatory drugs, and proteasome inhibitors have been shown so far. Anti-MAG neuropathy is accompanied by IgM monoclonal gammopathy. Distal dominant demyelinating neuropathy is a common feature of its neuropathy. Anti-MAG neuropathy is often refractory to conventional treatment such as steroid and immunoglobulin. Rituximab might be effective in some cases.