Anti-DPPX encephalitis was first identified in 2013. Patients with anti-DPPX encephalitis have autoantibodies directed against dipeptidyl-peptidase–like protein 6 (DPPX). DPPX is a subunit of voltage-gated potassium channels that are found on gut and brain neurons. These channels are one of the key components in generation and propagation of electrical impulses in the gut and nervous system.
This disease usually effects middle-aged men (median age 57 years).
Patients first develop diarrhea or constipation that can be severe and accompanied by weight loss. After several months or more, this is then followed by the development of agitation, hallucinations and memory difficulties (cognitive-mental deficits). Seizures, tremors and/or muscle twitching are also seen (CNS hyperexcitability).
The presence of the antibodies is determined in the cerebral spinal fluid (CSF) and serum. The MRI is often normal, while the CSF shows elevated white blood cell count and elevated protein level.
A tumor is rarely seen with this syndrome, although there have been cases of B-cell lymphoma described.
Anti-DPPX encephalitis is treated with first-line immunotherapy (corticosteroids and immunoglobulin / plasmapheresis). In case of ineffectiveness second-line therapy should be considered using Rituximab or cyclophosphamide.
Most patients show substantial improvement with immunotherapy. However, a relapse rate of 23% has been documented and commonly occurs during immunotherapy withdrawal.
Myrna Rosenfeld, MD, Institute for Biomedical Research (IDIBAPS) of the University of Barcelona, Spain, Adjunct Professor of Neurology at the University of Pennsylvania