[Iatrogenic neuropathies]

During the last few years the list of drugs capable of inducing a iatrogenic neuropathy has been considerably lengthened. Drug toxicity to peripheral nerves may be discovered at the experimental stage, but it is usually recognized after the drug has been launched on the market, hence the importance of pharmacovigilance. The responsibility of a drug for the occurrence of neuropathy may be difficult to prove, particularly when the drug is used in the treatment of a disease which, by itself, may be responsible for a lesion of the peripheral nervous system. Iatrogenic neuropathies are usually axonal, but some drugs produce a primary disorder in the myelin-Schwann cell couple. Schwann cell diseases may be induced by drugs, such as perhexiline maleate, amiodarone or chloroquine, which inhibit lysosomal enzyme activity. In such cases inclusions representing fat-loaded lysosomes can be detected in various tissues, and particularly in Schwann cells. In certain patients, notably those treated with gold salts, an immune mechanism might be responsible for neuropathy. Most drug-induced neuropathies are due to a primary lesion of the neuron which is more often an axonopathy than a neuronopathy. It is usually a retrograde distal axonopathy the occurrence of which is attributed to a disorder of the fast retrograde axonal flow. In a few cases, the finding of a biochemical mechanism perturbing the axonal flow may help in preventing the occurrence of a iatrogenic neuropathy.