Diseases of diverse etiology can be correlated to the term "polyneuropathy"(PNP). The pathogenesis may be of inflammatory, autoimmune, metabolic, toxic or hereditary nature. Careful clinical and electrodiagnostic assessment, with attention to the pattern of involvement and the types of nerve fibers most affected, narrows the differential diagnosis and helps to focus the laboratory evaluation. Beside the frequent genetic etiologies in PNP (pmp22, MFN2) one cause of a polyneuropathy may be a hereditary amyloidosis. This term describes the accumulation of misfolded protein in the interstitial space. The abnormal accumulation of β-fibrils can be detected histologically by Congo pink staining. Aside from acquired amyloidotic neuropathies (e.g. PNP caused by AL-amyloidosis there are also hereditary amyloidotic neuropathies.