Different profiles of onion bulb in CIDP and CMT1A in relation to extracellular matrix.

Hypertrophic neuropathy is usually intractable, and chronic inflammatory demyelinating polyneuropathy (CIDP) and Charcot-Marie-Tooth disease Type 1A (CMT1A) are the representative disorders. The two disorders are sometimes confused both clinically and pathologically. The aim of this study was to clarify the differences in the pathology of large onion bulbs, focusing on the extracellular matrix (ECM) proteins. Nine patients with CIDP and 14 with CMT1A were included. The opened interspaces in OB were frequently shown in CMT1A patients. In CIDP, interspaces of OB packed with collagen fibers were prominent. The mean ratio of opened OB was significantly increased in CMT1A (37.9%) compared to CIDP patients (10.6%) (p = 0.003). Among the ECM examined, tenascin-C (TNC) showed a distinct difference in the pattern of immunoreactivity of OB. The mean ratio of OB showing TNC immunoreactivity was significantly larger in CIDP (29.7%, p = 0.005) than in CMT1A (5.0%). TNC immunoreactivity was confined to the area around myelin sheaths in CMT1A. The increased deposition of collagen fibers in CIDP suggests the activity of nerve regeneration. TNC expression in Schwann cell lamellae comprising OB may also suggest the activity of regeneration. Schwann cell phenotypes in CIDP may be different from CMT1A regarding the production of ECM proteins.