Clinical, electrophysiological and immunological study of peripheral nerves in Egyptian patients with monoclonal gammopathies.

Monoclonal antibodies are found in approximately 10% of patients with peripheral neuropathy (PN) of unknown etiology. Several autoantibodies, including anti-MAG (myelin-associated glycoprotein) antibodies, have been reported to induce neuropathy. It has been suggested that over 50% of patients with PN and IgM monoclonal gammopathy (MG) have anti-MAG IgM antibodies in their sera. This work aimed at studying the frequency and characteristics of PN in a group of Egyptian patients with MGs and to estimate the serum level of anti-MAG antibodies and its relationship to peripheral nerve dysfunction. Forty patients with MGs were enrolled in the study. Their mean age was 56.65 ± 8.55 years. There were 17 males and 23 females. Patients were subjected to complete general and neurological examination, laboratory investigations including serum LDH, β2 microglobulin, serum protein electrophoresis, urinary Bence-Jones protein, bone marrow aspiration and/or trephine biopsy, quantitative estimation of serum IgM and IgG by nephelometry, detection of anti-MAG antibodies by indirect immunofluorescence, radiological assessment and nerve conduction study of both upper and lower limbs. Clinical and electrophysiological evidences of PN were found in 32 (80%) out of the 40 patients with MG. Twenty-five patients (62.5%) had distal symmetrical polyneuropathy and seven (17.5%) had mononeuritis or mononeuritis multiplex. The majority of patients (65%) had sensory or predominantly sensorimotor polyneuropathy. The neuropathy was mainly demyelinating in 22 patients (55%) and axonal in the other 10 (25%) patients. Anti-MAG antibodies were positive in nine patients (22.5%) and six of them (66.6%) had PN. The latter was predominantly demyelinating motor neuropathy in 4 and axonal in the remaining 2. However, the relationship between the presence of anti-MAG antibodies and the development and type of PN was not statistically significant. Anti-MAG showed significant association with IgM level (P = 0.003**) and the MG subtypes: Waldenström's macroglobulinemia (WM) and monoclonal gammopathy of undetermined significance (MGUS) (P = 0.004**). The present study showed high frequency (>60%) of distal symmetrical polyneuropathy in Egyptian patients with MG. The neuropathy was predominantly sensory and demyelinating. Anti-MAG antibodies were detected only in 22.5% of the patients, especially those with WM and MGUS and were associated with more motor and demyelinating neuropathy. We recommend that patients with chronic polyneuropathies should be evaluated for underlying plasma cell dyscrasia.