Walsh & Hoyt: Diagnosis

The diagnosis of CIDP is made by the combination of appropriate clinical, electrophysiologic, and CSF findings. A biopsy, usually of the sural nerve, may be required to confirm the diagnosis and to distinguish the condition from other types of chronic polyneuropathy, such as multifocal motor neuropathy (MMN), chronic idiopathic axonal polyneuropathy (CIAP), POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M proteins, and skin changes), IgM gammopathy, and multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy. Other disorders to be considered in patients suspected of having CIDP include hereditary polyneuropathies, chronic demyelinating polyneuropathies associated with systemic diseases such as plasma cell dyscrasias and paraproteinemias, and toxic polyneuropathy of diphtheria. This highlights that even when a diagnosis of CIDP seems clear, a continued search for an underlying etiology may be appropriate.