Abstract: Objective To explore the clinical characteristics of acute disseminated encephalomyelitis (ADEM) with anti-contactin-associated protein-like 2 (Caspr 2 ) antibody associated autoimmune encephalitis. Methods The clinical data of ADEM complicated with anti-Caspr 2 antibody associated autoimmune encephalitis in a child were analyzed retrospectively. Results A 7 -year- and 10 -month-old girl was admitted to hospital due to fever and mental distress. During the course of the disease, she developed clinical symptoms including seizures, lethargy, coma, cognitive impairment, mental personality changes, insomnia, and neuropathic pain and so on. Cranial magnetic resonance imaging (MRI) showed patchy-like high-signal shadows in bilateral cerebral hemispheres with T 2 WI and FLAIR sequences. On the 4 th day of the disease course, the cerebrospinal fluid Caspr 2 antibody was negative, and the cerebrospinal fluid Caspr 2 antibody turned positive on the 21 st day of the disease course, and ADEM complicated with anti-Caspr 2 antibody associated autoimmune encephalitis was diagnosed. The clinical symptoms and cranial MRI of the children recovered well after the treatment with glucocorticoid and immunoglobulin plus plasmapheresis. Conclusions ADEM complicated with anti-Caspr 2 antibody associated autoimmune encephalitis is rare. Prompt completion of blood and cerebrospinal fluid autoimmune encephalitis-related antibody examinations, head MRI and other related auxiliary examinations are conducive to timely diagnosis and treatment and improvement of prognosis.

Key words: acute disseminated encephalomyelitis; autoimmune encephalitis; anti-Caspr 2 antibody; clinical characteristic; child