Prevalence of hereditary transthyretin amyloidosis in CIDP patients with red flags: a multicenter genetic screening and misdiagnosis analysis

Background: Hereditary transthyretin amyloidosis (ATTRv) is a rare, multisystemic disorder often presenting with peripheral neuropathy and can be misdiagnosed with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), especially in non-endemic areas. While clinical red flags have been proposed to aid diagnosis, their predictive value remains uncertain. This study prospectively assessed the prevalence of TTR variants in CIDP patients with red flags for ATTRv and retrospectively analyzed features of genetically confirmed ATTRv cases initially misdiagnosed as CIDP. Methods: Thirteen Italian tertiary neuromuscular centers consecutively screened CIDP patients with at least one red flag for TTR gene variants. A retrospective analysis was also conducted on ATTRv patients initially misdiagnosed as CIDP, comparing clinical, electrophysiological, and treatment response features to confirmed CIDP cases. Results: No TTR variants were identified among 124 screened CIDP patients despite 65% presenting with ≥ 2 red flags and 14% not responding to standard therapies. Among 17 retrospectively identified ATTRv patients, 5 (29%) met electrodiagnostic criteria for CIDP. In nearly half, CIDP was diagnosed without fulfilling electrodiagnostic criteria or obtaining appropriate supportive investigations. Compared to confirmed CIDP patients, ATTRv cases exhibited significantly more red flags, later onset, more insidious and distal presentations, a progressive course, lower rates of demyelination criteria fulfillment, and no response to immunomodulatory therapy. Conclusions: Red flags alone have limited predictive value in specialized settings. However, ATTRv should be considered in distal, progressive, treatment-resistant neuropathies, especially with multisystem features. Greater diagnostic rigor and increased awareness in non-specialist settings is essential to reduce misdiagnosis and improve access to therapy.