Similar Disorders to CIDP
Carol L. Koski, M.D. and Richard A. Lewis, M.D., Principal Authors
Several disorders are similar to chronic inflammatory demyelinating polyneuropathy (CIDP ), but considered distinct from CIDP.
Multifocal Motor Neuropathy (MMN)
Multifocal Motor Neuropathy (MMN) is a pure motor disorder in which there is a multifocal attack on the motor nerve fibers of individual peripheral nerves. Essentially, it is a pure motor mononeuropathy multiplex. The characteristic feature of MMN is conduction block with or without other electrophysiologic features of segmental demyelination. MMN is considered distinct from CIDP because:
- In a significant number of MMN patients (35-83%) there are high titers of antibodies directed against GM1 ganglioside.
- CSF protein is not elevated
- Reflexes are lost only in a multifocal fashion
- MMN does not respond to corticosteroids or plasmapheresis
Lewis-Sumner Syndrome (L-SS)
In contrast, L-SS, a multifocal sensorimotor mononeuropathy multiplex, which is also characterized by multifocal persistent conduction block and is considered a variant of CIDP. L-SS tends to have higher CSF protein, no anti-GM1 antibodies and responds to treatment in a similar way to patients with symmetric CIDP. As such, except for the multifocal features, no other distinctions between L-SS and CIDP have been found.
Paraproteinemic Neuropathies
IgM is distinct from CIDP but IgA and IgG are not. There are strong reasons why IgM neuropathies are considered distinct from CIDP while patients with neuropathies and IgA and IgG paraproteins are considered to be variants of CIDP. IgG paraproteins can be seen in the normal aging population unrelated to any clinical disorder. Studies have shown that there is no increase in the incidence of neuropathy in people with IgG paraproteins. This also appears to be the case with IgA paraproteins. However, the incidence of neuropathy, particularly demyelinating neuropathies is significantly increased with IgM paraproteins. Thus, a patient with demyelinating neuropathy may have a coincidental IgG or IgA paraprotein but it is much more likely that an IgM paraprotein is related. It should be noted that IgA and IgG paraproteins may be seen in POEMS which should be carefully considered.
Approximately 50% of patients with demyelinating neuropathy and an IgM paraprotein have high titer antibodies directed against Myelin Associated Glycoprotein. These patients have a distinct clinical presentation of distal sensory predominant symptoms, distinct electrophysiologic features of distal accentuated conduction slowing, and a distinct lack of response to most immunosuppressive treatments. It is therefore very clear that anti-MAG neuropathies are distinct from CIDP.
The issue with other IgM neuropathies is less clear. The EFNS/PNS guidelines point to separating anti-MAG neuropathies from CIDP but not separating other IgM neuropathies. However, the literature tends not to show any differences between patients with distal sensory predominant neuropathy and IgM paraproteins and anti-MAG antibodies and those without the antibodies. Both groups of IgM neuropathies have distal accentuated slowing and poor response to immunosuppression. For that reason, many authors believe that all demyelinating neuropathies with IgM paraproteins should be considered distinct from CIDP.
Other peripheral neuropathies
Other systemic conditions or infectious agents that cause inflammatory peripheral neuropathy include- Waldenström's macroglobulinemia,
- collagen vascular disease,
- immune complex disease,
- cryoglobulinemia associated with hepatitis,
- Borrelia burdorferi,
- Mycobacterium leprae, and
- Trypanosoma cruzi.
