Blurred Lines – Is the distinction between CIDP and CMT always clear?

Introduction: Charcot-Marie-Tooth disease (CMT) is a group of inherited sensorymotor neuropathies with variable age of onset, clinical and neurophysiological patterns but often with a chronic slow progression. Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated neuropathy with a relapsing clinical course and typically good response to corticosteroids or other therapies. The distinction between these two conditions can be made with aid of clinical history, neurophysiological studies and genetic testing in the vast majority of cases. However, an overlap between them can occur. Methods: We describe four Brazilian patients under clinical follow-up at our service with genetic diagnosis of CMT and clinical and neurophysiological features compatible with a concurrent CIDP diagnosis. Results: Four cases of different CMT subtypes with co-occurrence of an immunemediated neuropathy compatible with CIDP were reported. The patients were all unrelated, two males and two females, age range from 3 to 45 years. The genetic mutations were the following: hemizygous pathogenic variant c.514C>T (p.Pro172Ser) in GJB1 gene (CMT1X), duplication of PMP22 gene (CMT1A), simple heterozygous pathogenic variant c.188_190delCCT (p.Ser64del) in MPZ gene (CMT1B) and homozygous pathogenic variant c.122T>C (p.Ile41Thr) in FIG4 gene (CMT4J). All four patients presented with relapsing or subacute worsening of neurological symptoms, demyelinating non-uniform features in neurophysiological studies including conduction blocks and elevated cerebrospinal fluid (CSF) protein levels without pleocytosis. Three patients (3/4) improved after treatment with corticosteroids, immunoglobulin or cyclophosphamide with variable clinical response. Conclusion: CMT and CIDP are different conditions involving the peripheral nervous system and the distinction between them usually is possible with the appropriate assessment. The overlap between them is possible and we report four cases with this association.