[Diagnostics of polyneuropathies].

Polyneuropathies are a heterogeneous group of peripheral nerve disorders with diverse causes and phenotypes. Structured, phenotype-oriented diagnostics are important for reliably identifying common and treatable triggers such as diabetes, alcohol, vitamin deficiency, or medication, and for distinguishing them from immune-mediated, paraneoplastic, or genetic neuropathies. Medical history, clinical examination, and electrophysiology usually provide the decisive clues. In addition, basic laboratory diagnostics, targeted immunological tests, and modern genetics are used for selected indications-such as for the question of sorbitol dehydrogenase (SORD) mutations and repeat expansion of replication factor C 1 (RFC1). Nerve ultrasound and biopsy have selected indications. Entities such as immune checkpoint inhibitor (ICI)-associated neuropathies and nitrous oxide induced myeloneuropathy are gaining in importance. Age-related physiological changes must always be taken into account.