Long-term follow-up of patients with chronic inflammatory demyelinating polyradiculoneuropathy, without and with monoclonal gammopathy.

We previously demonstrated differences in presentation and initial clinical course between patients with idiopathic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP-I) and those in whom CIDP was associated with a monoclonal gammopathy of undetermined significance (CIDP-MGUS). We now report the long-term follow-up of 69 patients with CIDP-I and 25 patients with CIDP-MGUS. (i) The clinical course was progressive in most of the CIDP-MGUS patients. CIDP-I patients were more likely to have a monophasic or relapsing course. (ii) Impairment developed more slowly in CIDP-MGUS than CIDP-I patients, with a longer time from onset of deterioration to peak impairment for each episode. (iii) Patients with CIDP-MGUS experienced less severe functional impairment and a lesser degree of measured weakness during their worst episode than did patients with CIDP-I. The primary source of functional impairment in many CIDP-MGUS patients was sensory. In contrast, the deficits in most patients with CIDP-I were primarily motor. (iv) CIDP-MGUS patients experienced a smaller degree of improvement to a poorer functional level after each episode than did patients with CIDP-I. (v) Most patients had a good outcome. However, the strength and functional scores at the time of last follow-up were significantly poorer in CIDP-MGUS than in CIDP-I patients. (vi) The disease was reclassified in seven patients; some patients with CIDP-I developed an MGUS, while some with CIDP-I or CIDP-MGUS developed multiple myeloma or a related malignant lymphoproliferative disease. These findings have implications for patient counselling and long-term prognosis, and underscore the need for long-term clinical and immunological monitoring.