Inflammatory neuropathies of the enteric nervous system.

Inflammatory neuropathy of the enteric nervous system is emerging as an important topic in the field of neurogastroenterology. Enteric ganglionitis can be either primary or secondary to a wide array of diseases (i.e., paraneoplastic, infectious, and neurological disorders) and is characterized by a dense infiltrate of inflammatory/immune cells mainly confined to the neural microenvironment. The clinical picture reflects the involved segment of the gastrointestinal tract (achalasia, gastroparesis, pseudo-obstruction, and megacolon). In these settings, symptoms may develop either acutely (frequently after a flulike episode in otherwise previously healthy individuals) or more slowly (e.g., in paraneoplastic syndromes). The inflammatory/immune response in enteric ganglionitis leads to neuronal dysfunction and degeneration over time and sometimes results in a complete loss of enteric neurons. The diagnosis of enteric ganglionitis is supported by detection of circulating antineuronal antibodies against select molecular targets, including Hu and Yo proteins, neurotransmitter receptors, and ion channels. Potential mechanisms involved in neuronal dysfunction include viral antigen expression in the enteric neural environment, molecular mimicry (onconeural antigens), and the role exerted by cellular and humoral autoimmunity. A short course of steroid or other immunosuppressive therapy has been shown to be helpful in the treatment of these conditions. This feature reinforces the concept of a cause/effect relationship of the immune-mediated insult damaging the enteric innervation. An increased awareness of the clinical features and the immunologic and neurodegenerative mechanisms of these forms of peripheral neuropathy is important to correctly diagnose this problem during the early stages of the disease process and to provide appropriate immunosuppressive therapies.