Immunohistochemical and ultrastructural classification of peripheral neuropathies with onion-bulbs.

By immunochemically and ultrastructurally identifying cellular components of onion-bulbs (Obs), this study attempts to delineate and classify types of hypertrophic neuropathies which are otherwise obscured by proliferation of the morphologically similar cells forming Obs. Fourteen cases with different forms of chronic localized or generalized hypertrophic neuropathy with Obs were retrospectively studied to include: one Dejerine-Sottas (D-S); two Charcot-Marie-Tooth (CMT); three chronic inflammatory demyelinating polyneuropathy (CIDP); one inflammatory localized hypertrophic mononeuritis (LHM); two perineuriomas (PNM); one traumatic amputation neuroma (TAN); one chronic diabetic neuropathy (CDN); two neurofibromas (NF); and one chronic arsenic polyneuropathy (AsPN). By immunostaining with 7 selected antibodies, we can distinguish at least 4 nosologically distinct types of neuropathy by identifying cellular components of given Obs: 1) primarily Schwann cells with no perineurial cells or macrophages in CMT or D-S, 2) predominantly Schwann cells, activated macrophages and a few fibroblasts in CIDP and LHM, 3) primarily perineurial and a few central Schwann cells with no macrophages in PNM and TAN, and 4) exclusively perineurial cells in the hamartomatous PNM associated with NF.