Paraproteinemia and neuropathy

Vasculitic Neuropathies

The classification of vasculitis and the clinical features of vasculitic neuropathy are reviewed. Vasculitic neuropathy usually presents with painful mononeuropathies or an asymmetric polyneuropathy of acute or subacute onset. Neurologists should categorize vasculitic neuropathy in terms of clinical features (eg, systemic or non systemic) and in terms of histopathology (eg, nerve large arteriole vasculitis or nerve microvasculitis). Systemic vasculitis should be classified further into one of the primary and secondary forms. Steroids and cytotoxic agents have been the mainstay of therapy for most forms of vasculitic neuropathy. Dosing, potential side effects, and management recommendations of conventional therapies are provided.

Paraproteinemic neuropathies

Paraproteinemic neuropathies comprise a diverse group of disorders that includes monoclonal gammopathy of undetermined significance, primary amyloidosis, multiple myeloma, cryoglobulinemia, POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein and skin changes) syndrome, and Waldenstrom macroglobulinemia. Various factors including hepatitis C virus, vascular endothelial growth factor, and an array of cytokines are implicated in the pathogenesis of these conditions. More recently, a variety of novel antibody specificities, and vasculitis, have also been described as contributory factors in the development of these neuropathies. Therapeutic approaches for paraproteinemic neuropathies have included administration of cytotoxic agents, steroids, interferon-alpha, intravenous immunoglobulin, radiation, bone marrow transplantation, and more recently, drugs such as rituximab and bevacizumab. In this article, we review some of the well-known features of these diseases, and highlight some of the more recent findings from the vast literature for these diseases.

An update on the classification and treatment of vasculitic neuropathy

Vasculitic neuropathy usually presents with painful mononeuropathies or an asymmetric polyneuropathy of acute or subacute onset. The disorder should be classified as being systemic or non-systemic. Systemic vasculitis should be further classified into one of the primary and secondary forms. Although specific treatment regimens vary among neurologists, basic principles can be applied. Corticosteroids and cytotoxic drugs have been the mainstay of treatment for most forms of vasculitic neuropathy. Here we discuss dosing, potential side-effects, and management recommendations of conventional treatments. New treatments showing promise include intravenous immunoglobulin and biological agents and trials of the newest treatments are being reviewed. Future trials should compare commonly used treatment regimens and better establish the efficacy of newer, potentially safer, treatments.

Immunotherapy of idiopathic inflammatory neuropathies

Evaluation of peripheral neuropathy is a common reason for referral to a neurologist. Recent advances in immunology have identified an inflammatory component in many neuropathies and have led to treatment trials using agents that attenuate this response. This article reviews the clinical presentation and treatment of the most common subacute inflammatory neuropathies, Guillain-Barré syndrome (GBS) and Fisher syndrome, and describes the lack of response to corticosteroids and the efficacy of treatment with plasma exchange and intravenous immunoglobulin (IVIG). Chronic inflammatory demyelinating polyneuropathy, although sharing some clinical, electrodiagnostic, and pathologic similarities to GBS, improves after treatment with plasma exchange and IVIG and numerous immunomodulatory agents. Controlled trials in multifocal motor neuropathy have shown benefit after treatment with IVIG and cyclophosphamide. Also discussed is the treatment of less common inflammatory neuropathies whose pathophysiology involves monoclonal proteins or antibodies directed against myelin-associated glycoprotein or sulfatide. Little treatment data exist to direct the clinician to proper management of rare inflammatory neuropathies resulting from osteosclerotic myeloma; POEMS syndrome; vasculitis; Sjögren's syndrome; and neoplasia (paraneoplastic neuropathy).

Microvasculitic paraproteinaemic polyneuropathy and B-cell lymphoma

Microvasculitis may play a greater part in the pathogenesis of paraproteinaemic neuropathies than is generally recognised, producing tissue destruction by convergent immune and physical mechanisms. We present a patient with a clinical syndrome of mononeuritis multiplex and a circulating IgM lambda paraprotein, in whom bone marrow aspiration revealed a lymphoplasmacytoid lymphoma. Microvasculitic changes were present in the first nerve biopsy, and the second showed extensive destruction of neural architecture and deposition of IgM-related material. A 2-stage pathogenic cascade is postulated and explored with a review of the relevant literature.

Treatment recommendations in Waldenstrom's macroglobulinemia: consensus panel recommendations from the Second International Workshop on Waldenstrom's Macroglobulinemia

This presentation represents consensus recommendations for the treatment of patients with Waldenstrom's macroglobulinemia (WM), which were prepared in conjunction with the second International Workshop held in Athens, Greece during September 2002. The faculty adopted the following statements for the management of patients with Waldenstrom's macroglobulinemia: (1) Alkylating agents, nucleoside analogues, and rituximab are reasonable choices for first line therapy of WM. (2) Both cladribine and fludarabine are reasonable choices for the therapy of WM. (3) Combinations of alkylating agents, nucleoside analogues, or rituximab should at this time be encouraged in the context of a clinical trial. (4) In WM, rituximab can cause a sudden rise in serum IgM and viscosity levels in certain patients, which may lead to complications, therefore close monitoring of these parameters and symptoms of hyperviscosity is recommended for WM patients undergoing rituximab therapy. (5) For relapsed disease, it is reasonable to use an alternate first line agent or re-use of the same agent; however, since autologous stem cell transplantation may have a role in treating patients with relapsed disease it is recommended that for patients in whom autologous transplantation is seriously being considered, exposure to alkylator or nucleoside analogue drugs should be limited. (6) Combination chemotherapy for patients who can tolerate myelotoxic therapy, thalidomide alone or with dexamethasone, can reasonably be considered to have relapsed. (7) Autologous stem cell transplantation may be considered for patients with refractory or relapsing disease. (8) Allogeneic transplantation should only be undertaken in the context of a clinical trial. (9) Plasmapheresis should be considered as interim therapy until definitive therapy can be initiated. (10) Rituximab should be considered for patients with IgM-related neuropathies. (11) Corticosteroids may be useful in the treatment of symptomatic mixed cryoglobulinemia. (12) Splenectomy is rarely indicated but has been used to manage painful splenomegaly and hypersplenism.

Hepatitis C: a review of its neurologic complications

BACKGROUND

Hepatitis C viral (HCV) infection is common in the general population and can cause disease in the nervous system. This article reviews the neurologic complications associated with this virus.

REVIEW SUMMARY

A vasculitic neuropathy is the most firmly linked neurologic illness associated with HCV infection. This type of neuropathy occurs frequently in the presence of cryoglobulinemia. HCV is considered the most common cause of cryoglobulinemia. Other types of neuropathy have been rarely reported with HCV infection and this association is less firm. In the central nervous system, vasculitis causing stroke appears to complicate HCV infection, usually in the setting of cryoglobulinemia. Several reports of myelitis, encephalitis,lymphoma are reviewed. HCV may be the etiologic virus of progressive encephalomyelitis with rigidity; a rare disorder similar to stiff-man syndrome although different because it is progressive and fatal. Treatment of the neurologic complications associated with HCV infection is summarized.

CONCLUSIONS

HCV infection is being increasingly recognized as a probable cause of a variety of neurologic disorders. Systematic study of the various therapeutic options remains unexplored.

Paraproteinemic neuropathies

The occurrence of a peripheral neuropathy (PN) in association with a monoclonal gammopathy is quite common and suggests that monoclonal proteins may play a pathogenetic role in peripheral nervous system damage. In fact, paraproteinemic PN constitute an heterogeneous group of disorders related to various pathogenetic factors, and the histopathologic features in peripheral nerve biopsies differ from one condition to another. In several well defined disorders, the responsibility of the monoclonal component in the development of the PN has been evidenced. This is the case for most of the PN associated with an IgM monoclonal gammopathy, either a monoclonal gammopathy of undetermined significance (MGUS) or Waldenstrom's macroglobulinemia. The responsibility of the monoclonal protein in the occurrence of amyloid neuropathy related to multiple myeloma is also recognized. However, most IgG or IgA MGUS, as well as the monoclonal component in POEMS syndrome, have an uncertain causal relationship with the neuropathy. PN associated with monoclonal cryoglobulin (type 1) are occasional and differ from those associated with mixed cryoglobulins (types 2 or 3).

Neuropathy and monoclonal gammopathy

The association of neuropathy with monoclonal gammopathy has been known for several years, even if the nosological position of these neuropathies is still debated. Similarly unsettled is the pathogenetic role and diagnostic relevance in clinical practice of the antineural antibodies frequently associated with monoclonal gammopathies of undetermined significance of IgM isotype, as well as the most effective therapy (if any) to be used in these patients. Over the past 12 months these issues have been addressed in several papers whose results will be critically reviewed here.

The role of macrophages in immune-mediated damage to the peripheral nervous system

Macrophage-mediated segmental demyelination is the pathological hallmark of autoimmune demyelinating polyneuropathies, including the demyelinating form of Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy. Macrophages serve a multitude of functions throughout the entire pathogenetic process of autoimmune neuropathy. Resident endoneurial macrophages are likely to act as local antigen-presenting cells by their capability to express major histocompatibility complex antigens and costimulatory B7-molecules, and may thus be critical in triggering the autoimmune process. Hematogenous infiltrating macrophages then find their way into the peripheral nerve together with T-cells by the concerted action of adhesion molecules, matrix metalloproteases and chemotactic signals. Within the nerve, macrophages regulate inflammation by secreting several pro-inflammatory cytokines including IL-1, IL-6, IL-12 and TNF-alpha. Autoantibodies are likely to guide macrophages towards their myelin or primarily axonal targets, which then attack in a complement-dependent and receptor-mediated manner. In addition, non-specific tissue damage occurs through the secretion of toxic mediators and cytokines. Later, macrophages contribute to the termination of inflammation by promoting T-cell apoptosis and expressing anti-inflammatory cytokines including TGF-beta1 and IL-10. During recovery, they are tightly involved in allowing Schwann cell proliferation, remyelination and axonal regeneration to proceed. Macrophages, thus, play dual roles in autoimmune neuropathy, being detrimental in attacking nervous tissue but also salutary, when aiding in the termination of the inflammatory process and the promotion of recovery.