Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common chronic treatable neuropathy in the Western world with a prevalence of 1–2 per 100,000 (Lunn et al. 1999; McLeod et al. 1999). It is the chronic variety of the inflammatory demyelinating neuropathies, of which the Guillain–Barré syndrome (GBS) is the acute form. Because it is treatable, CIDP needs to be considered in the differential diagnosis whenever a patient presents with an acquired chronic or progressive neuropathy. The inflammatory demyelinating neuropathies are characterised pathologically by multifocal areas throughout the peripheral nervous system (PNS) of inflammatory infiltrates associated with demyelination. When demyelination is assessed by the study of teased nerve fibres it is seen to be segmental, i.e. by and large restricted to the territory of individual Schwann cells (Figure 10.1). This characteristic pathological description suggests that the myelin loss, which occurs in these neuropathies, results from some insult which targets Schwann cells rather than the myelin itself.

Despite considerable advances in treatment strategies, which have developed effective therapies for a majority of patients, the pathogenic mechanisms which disrupt Schwann cell function resulting in demyelination remain unknown in most patients. It is likely moreover that CIDP, like GBS, is comprised of a number of different subtypes, and the study of patients within these homogenous subgroups may permit the recognition of meaningful patterns of pathogenicity. To date, research into CIDP and indeed its acute counterpart GBS has centred largely around the animal model experimental autoimmune neuritis (EAN).