A case report of complement C4B deficiency in a patient with steroid and IVIG-refractory anti-NMDA receptor encephalitis
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CASE REPORT
Open Access
A case report of complement C4B deficiency in a patient with steroid and IVIG-refractory anti-NMDA receptor encephalitis Gilbert T. Chua1, Danlei Zhou2, Alvin Chi Chung Ho1, Sophelia Hoi Shan Chan1, Chack Yung Yu2 and Yu Lung Lau1*
Abstract Background: Complement C4A or C4B deficiency has never been reported in autoantibody-associated encephalitides patient. Here we present a case of anti-N-methyl- D-aspartate (NMDA) receptor encephalitis associated with homozygous C4B deficiency, who did not respond to intravenous immunoglobulin and pulse methylprednisolone but plasmapheresis and rituximab. Case presentation: A fourteen-year-old boy presented to our unit with subacute onset of behavioral changes and confusion, and was later confirmed to be anti-NMDA receptor encephalitis. He was initially managed with intravenous immunoglobulin (IVIG) and pulse methylprednisolone but did not achieve any clinical improvement. Seven sessions of plasmapheresis was commenced with remarkable improvement after the second session, and was followed by four doses of rituximab. His neurological and cognitive functioning gradually returned to baseline. Immunological investigations demonstrated persistently low C4 levels below 8 mg/dL. A more in-depth complement analysis of the patient and his family showed that he has homozygous C4B deficiency. Genetic analysis revealed that the index patient has homozygous deficiency in complement C4B and he carries one nonfunctioning mutant C4B gene inherited from his mother. Conclusions: Low levels of serum C4 correlate with reduced functions of the classical and lectin pathways, leading to the impairment of immune-complexes removal. Plasmapheresis ameliorates complement deficiency and removes the offending immune-complexes leading to clinical improvement that was not achieved by IVIG and steroids. We postulate that serum C4 levels may serve as a biomarker for the need of plasmapheresis upfront rather than only after non-response to steroid and IVIG in treating anti-NMDA-receptor encephalitis. Keywords: Anti-NMDA receptor encephalitis, Homozygous C4B deficiency, Plasmapheresis
* Correspondence: [email protected] 1 Department of Paediatrics and Adolescent Medicine, Queen Mary Hospital, The University of Hong Kong, Room 106, 1/F, New Clinical Building, 102 Pokfulam Road, Pokfulam, Hong Kong Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and you
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