Sarcoid neuropathy: clinico-pathological study of 4 new cases and review of the literature.

There are several reviews devoted to neurosarcoidosis and a few reports restricted to sarcoid neuropathy. Since 1989, we have investigated 4 new cases of sarcoid neuropathy, 1 with chronic sensory motor neuropathy (CSMN), another with painful neuropathy and 2 with atypical chronic inflammatory demyelinating polyneuropathy (CIDP). In each case, biopsy specimens from the superficial peroneal nerve and peroneus brevis muscle were taken by the same cutaneous incision and studied on paraffin sections, semi-thin sections and under electron microscope. We compared neuropathological findings from our 4 cases with those from 34 well-studied nerve biopsies previously reported in the literature, and which concerned 16 cases of CSMN, 13 cases ofmononeuropathy multiplex, 2 cases of painful neuropathy and three cases of CIDP. In all of these 38 cases of sarcoid neuropathy, the characteristic noncaseiting granulomas (NCG) were observed on the nerve in 11 cases, on the muscle alone in 5, on both muscle and nerve in 10, and in the nerve and another parenchyma in 4. In the 8 remaining cases, NCG were observed in another parenchyma, mainly lung or lymph nodes. Moreover, necrotizing vasculitis was present in nerve biopsies from 8 cases and microvasculitis without obvious necrosis in 2 others. Nerve fiber lesions, which are mainly axonal, are probably related to mechanical compression by NCG and/or to an ischemic process due to vasculitis. Cytokines and immune factors may also play a role, especially in certain cases with a clinical presentation of CIDP.