Misdiagnosis and diagnostic pitfalls of chronic inflammatory demyelinating polyradiculoneuropathy

OBJECTIVE To determine the frequency of over- and underdiagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and to identify related diagnostic pitfalls. METHODS Retrospective study of Dutch patients referred to the Erasmus University Medical Centre Rotterdam between 2011-2017 with either (1) a diagnosis of CIDP or (2) another diagnosis that was revised to CIDP. We used the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) 2010 diagnostic criteria for CIDP to classify patients in three groups: overdiagnosis, underdiagnosis or confirmed diagnosis of CIDP. Clinical and laboratory features, and treatment history were compared between groups. RESULTS A referral diagnosis of CIDP was revised in 32% (31/96) of patients (overdiagnosis). Of 81 patients diagnosed with CIDP, 16 (20%) were referred with another diagnosis (underdiagnosis). In the overdiagnosed patients, 20% of muscle weakness was asymmetric, 48% lacked proximal muscle weakness, 29% only had distal muscle weakness, 65% did not fulfil the electrodiagnostic criteria for CIDP, 74% had an elevated CSF protein level, and 97% had another type of neuropathy. In the underdiagnosed patients, all had proximal muscle weakness, 50% had a clinically atypical CIDP, all fulfilled the electrodiagnostic criteria for CIDP, and 25% had an increased CSF protein level. CONCLUSION Over- and underdiagnosis of CIDP is common. Diagnostic pitfalls include lack of attention to proximal muscle weakness as a diagnostic hallmark of CIDP, insufficient recognition of clinical atypical phenotypes, overreliance on CSF protein levels, misinterpretation of nerve conduction studies and poor adherence to electrodiagnostic criteria, and failure to exclude other causes of polyneuropathy.