Anti‐kelchlike protein 11 antibody‐associated encephalitis: Two case reports and review of the literature

Abstract

AbstractBackground and purposeKelchlike protein 11 antibodies (KLHL11‐IgGs) were first described in 2019 as a marker of paraneoplastic neurological syndromes (PNSs). They have mostly been associated with testicular germ cell tumors (tGCTs).MethodsTwo patients with KLHL11‐IgG encephalitis are reported, and the literature is comprehensively reviewed.ResultsPatient 1 had been in remission from a tGCT 10 years prior. He developed episodic vertigo and diplopia progressing over a few days. Treatment with corticosteroids (CSs) was started a few days after symptom onset. Patient 2 had transient diplopia, which resolved spontaneously. Visual problems persisted for 7 months, when he additionally developed a progressive cerebellar syndrome. One year after onset, CS treatment was started. Initial magnetic resonance imaging was unremarkable in both patients, but analysis of cerebrospinal fluid (CSF) revealed chronic inflammation. KLHL11‐IgG was positive in both patients (Patient 1 only in CSF, Patient 2 in serum). Neoplastic screening has so far not revealed any signs of active underlying malignancy. We found 15 publications of 112 patients in total with KLHL11‐IgG encephalitis. Most patients (n = 82) had a cerebellar syndrome with or without signs of rhombencephalitis. The most common symptoms were ataxia (n = 82) and vertigo (n = 47), followed by oculomotor disturbances (n = 35) and hearing disorders (n = 31). Eighty of 84 patients had a GCT as an underlying tumor.ConclusionsOur cases demonstrate classical symptoms of KLHL11‐IgG encephalitis. Early diagnosis and therapy are imperative. As with other PNSs, clinical awareness is needed and further studies are required especially in regard to therapeutic management.