Polyneuropathy associated with IgA monoclonal gammopathy: a hypothesis of its pathogenesis

A case of severe chronic inflammatory demyelinating polyradiculoneuropathy with monoclonal gammopathy of undetermined significance with alternating immunoglobulin class to IgM from IgA

A 71-year-old woman with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with IgA-λ monoclonal gammopathy of undetermined significance (MGUS) showed the acute development of tetraplegia, respiratory failure, and a marked fluctuation of the blood pressure. Intravenous (IV) high-dose steroid therapy (methylprednisolone: 1 g/day × 3 days), followed by oral prednisolone (PSL) (40 mg/day), and IV immunoglobulin (IVIg, 0.4 g/kg/day × 5 days) administrations resulted in the amelioration of these symptoms. However, they soon relapsed, which eventually led to complete tetraplegia and the need for mechanical ventilation. At this time, serum components of IgA-λ and IgM-λ were biclonally positive. Seven courses of plasma exchange and the alternative administration of dexamethasone (12 mg/day) and methtorexate (15 mg/week) were conducted, but with no significant improvement. Nine months after admission, she showed totally-locked in syndrome. Cryo-preserved serum obtained at this time showed high titers of IgM class antibodies against ganglioside (GD3 +++, GT1a ++++, GT1b ++, GQ1b +++, and GD1b +++), which had been negative on admission. Biopsy of the left sural nerve showed moderate reductions of large and small myelinated fibers with no inflammation, no depositions of amyloid, IgG, IgA, or IgM, and teased fiber findings revealed neither myelin ovoids nor segmental demyelination. Alternatively, melphalan at 5 mg and PSL at 32 mg were administered, with no amelioration, while serum IgA-λ monoclonal protein diminished, and IgM-λ M protein positivity was continuously observed. She frequently developed sepsis; therefore, we could no longer continue any immunosupressive therapies, but monthly IVIg administrations were given. Twelve months after admission, her neurological symptoms gradually improved and she was weaned off of mechanical ventilation. Eighteen months after admission, her muscle strength corresponded to 2 on manual muscle testing, and wheelchair transfer became possible. To the best of our knowledge, the present case is the first report of CIDP with MGUS showing an alternating immunoglobulin class.

Polyneuropathy associated with IgG/IgA monoclonal gammopathy: a clinical and electrophysiological study of 15 cases

Peripheral neuropathy has been widely reported in patients with monoclonal gammopathy (MG), more frequently immunoglobulin M (IgM) or IgG than IgA. Nevertheless, it remains unclear whether this association has clinical or pathogenic relevance. In order to clarify the possible role of IgG/IgA MG in neuropathy, we studied the clinical and electrophysiological features of 15 consecutive patients with polyneuropathy and IgG/IgA-MG, and compared them to those of 40 patients with polyneuropathy associated with IgM-MG, previously reported. Nine middle-aged patients (60%) had a chronic progressive or relapsing demyelinating polyneuropathy (DP) that was clinically and electrophysiologically indistinguishable from classic chronic inflammatory demyelinating polyneuropathy (CIDP) and frequently responded to immunosuppressive treatments, both characteristics supporting a dysimmune process. Six older patients (40%) had a chronic axonal distal polyneuropathy similar to the so-called chronic cryptogenic sensory polyneuropathy: there was no clear relationship with the MG in these patients and the response to immunosuppressive treatments was poor. Several features allowed us to distinguish between polyneuropathies associated with IgG/IgA-MG (IgG/IgA-PN) considered together and polyneuropathies associated with IgM-MG (IgM-PN). In the first group, the proportion of patients with a predominantly sensory clinical picture (27%) was less than that in the second group (75%), and there were fewer changes in nerve conduction studies. In addition, we found that the nine patients with DP associated with IgG/IgA-MG (IgG/IgA-DP) differed from the 31 with DP associated with IgM-MG (IgM-DP): clinical and electrophysiological studies clearly showed that the demyelinating pattern was more heterogeneous in IgG/IgA-DP than in IgM-DP. The spectrum of polyneuropathies associated with IgG/IgA-MG is heterogeneous, including DP, which is similar to classic CIDP, and axonal polyneuropathy, in which the pathogenic role of the MG remains elusive. In addition, IgG/IgA-DP differ from IgM-DP on clinical and electrophysiological grounds, suggesting probable different physiopathological mechanisms.

Multiple antibodies to nerve glycoconjugates in a patient with neuropathy and monoclonal IgA gammopathy

Several immunological abnormalities were found in a patient with mixed axonal and demyelinating neuropathy in association with a prominent monoclonal IgA lamda band in his serum. He had antibodies to the major LM1 ganglioside of human nerve that were restricted to the IgA class, but they were polyclonal and distinct from the major monoclonal IgA component. He also had a low level of a monoclonal IgM lamda antibody to the myelin-associated glycoprotein and sulfate-3-glucuronyl paragloboside that was not detected by routine immunofixation. The observations made on this complex patient, are presented in the context of emphasizing that immunological reactivities to neural antigens that are not due to the principal monoclonal antibody may be present in patients with neuropathy in association with gammopathy.

Polyneuropathy associated with IgA monoclonal gammopathy of undetermined significance

Although polyneuropathies associated with IgM and IgG monoclonal gammopathies have been well described, polyneuropathy with IgA monoclonal gammopathy of undetermined significance (MGUS) is less commonly seen and has not been well studied. We reviewed the clinical and electrodiagnostic features of 5 such patients, and the sural nerve biopsy findings in 4 of them. One patient was diabetic, while 4 were free of other diagnoses commonly associated with neuropathy. Clinical presentations were varied. Electrodiagnostic and histological studies ranged from primary demyelination to primary axon loss to a mixed axonal/demyelinating picture. Three patients who were treated appeared to respond to prednisone or intravenous gamma globulin, despite clear clinical, electrodiagnostic, and histological differences. We conclude that the polyneuropathy associated with IgA MGUS is heterogeneous, similar to that in IgM and IgG MGUS. A trial of immunomodulating therapy appears to be warranted in such patients if the neuropathy is sufficiently severe.

Peripheral neuropathy in monoclonal gammopathy of undetermined significance: prevalence and immunopathogenetic studies

In an unselected series of patients with monoclonal gammopathy of undetermined significance (MGUS) we found neuropathy in 2 of 34 patients with IgG (6%), 2 of 14 with IgA (14%), and 8 of 26 with IgM MGUS (31%). The neuropathy was subclinical in 6 patients (1 IgG, 1 IgA, and 4 IgM). Patients with IgG or IgA MGUS had a prominent motor impairment with electrophysiologic and morphologic findings suggestive of predominant axonal degeneration. No deposit of the M-protein in sural nerve and no reactivity of the M-protein with nerve was detected in these patients. Patients with IgM MGUS had a prominent sensory impairment with evidence of predominant demyelination. In 6 of these patients the M-protein reacted with the myelin-associated glycoprotein (MAG). The higher prevalence of neuropathy in patients with IgM MGUS may be related to the frequent reactivity of IgM M-proteins with MAG.

IgG monoclonal proteins from patients with axonal peripheral neuropathies bind to different epitopes of the 68 kDa neurofilament protein

We describe three patients with a sensorimotor axonal polyneuropathy and an IgG M-protein that binds to a 68 kDa axonal protein identified as the low molecular weight neurofilament protein (NF-L). The immunological studies revealed that the M-proteins have different target epitopes: one is phosphorylated and the other two are nonphosphorylated. One of the nonphosphorylated epitopes is common to other intermediate filaments, such as desmin and vimentin.