2445 A rare case of Erdheim-Chester Disease associated with anti-GABA-B antibodies

• Published in: BMJ neurology open 2022-08, Vol.4 (Suppl 1), p.A63-A63
• Main Authors: Dunkerton, Sophie, Penninkilampi, Ross, Beadnall, Heidi, Fulham, Michael, Jankelowitz, Stacey, Ahmed, Rebekah, Thayer, Zoe, Halmagyi, Michael, Abadir, Edward
• Format: Article
• Language: English
• Subjects: Abstracts; Antibodies; Encephalitis
• ISSN: 2632-6140
• DOI: 10.1136/bmjno-2022-ANZAN.171

IntroductionEncephalitis associated with anti-GABA-B antibodies is a rare phenomenon which has been typically shown to manifest as a paraneoplastic process, usually associated with small-cell lung cancer. The present case is an unusual presentation of cognitive decline in the context of GABA-B antibody positivity in association with Erdheim-Chester disease (ECD).CaseA 71 year-old previously high-functioning female presented to the Emergency Department with an abnormal outpatient MRI brain. On further history, there had been a subtle decline in memory and disinhibited behaviour in a premorbidly highly intelligent woman. After extensive investigation, she was found to have positive serum GABA-B antibodies. The search for underlying malignancy was inconclusive. It was not until the orthopaedics team requested a plain X-ray of the femurs that the classic radiological features of Erdheim-Chester disease were revealed, which was confirmed on a bone biopsy. She was diagnosed with Erdheim-Chester disease associated with anti-GABA-B antibodies. Her BRAF v600E mutation was negative, and hence she was commenced on treatment with cobimetinib. Therapy initially produced minor improvement in simple attention and processing speed on neuropsychological assessment, but there continued to be a marked decline in orientation, learning and memory abilities. Unfortunately, the patient continued to suffer from marked cognitive and behavioural disturbance six months after receiving treatment.ConclusionThis is an unusual case of cognitive decline secondary to a paraneoplastic autoimmune encephalitis associated with ECD. The case serves as a reminder that ECD should be considered as a differential for patients who present with neurological symptoms.