[Clinicopathological features of neuropathy associated with IgG4-related disease].

The newly recognized entity IgG4-related disease (IgG4-RD) is characterized by an elevated IgG4 serum concentration, swelling of organ, and tissue infiltration by IgG4-positive plasma cells with fibrosis. IgG4-RD has been reported in various organs. In the field of neurology, hypophysitis and hypertrophic pachymeningitis have been known to be related to IgG4-RD, while reported patients with neuropathy manifesting features compatible to IgG4-RD. The features of IgG4-related neuropathy are characterized by sensory-motor neuropathy, mononeuritis multiplex pattern, and predominant involvement of distal portions of the lower extremities. In the sural nerve biopsy specimens, fibrosis and IgG4-positive plasma cell infiltration in the epineurium and decreased myelinated fiber density due to axonal degeneration were observed. IgG4-RD should be considered as the differential diagnosis of neuropathy.