Neuroinflammation in CTLA-4 Haploinsufficiency: Case Report of a New Variant with Remarkable Response to Targeted Therapy

Inborn errors of immunity (IEI) encompass a diverse group of genetic disorders that often present with complex and multifaceted clinical features, including neuroinflammation. CTLA-4 deficiency (CTLA-4d), caused by monoallelic germline mutations in the CTLA4 gene, manifests with autoimmune phenomena, lymphoproliferation, infections, and neurological involvement in up to 30% of patients, with a broad clinical spectrum, ranging from encephalitis to demyelination and lymphocytic infiltration. Imaging typically shows multifocal contrast-enhancing lesions. Early recognition of CTLA-4d is crucial to guide clinical management. Herein, we report the case of a 15-year-old girl presenting with severe multifocal neuroinflammatory lesions, recurrent infections, and systemic granulomatous disease. After extensive infectious and immunological workup, a heterozygous de novo CTLA4 variant c.394G>A_p.Glu132Lys was identified and its pathogenicity confirmed by transendocytosis functional assays. Based on the genetic diagnosis, the patient was started on abatacept, with brilliant clinical and radiological results after dose adjustment. This report describes a new pathogenic variant of the CTLA4 gene and highlights the importance of considering IEIs, such as CTLA-4d, in patients with unexplained severe neuroinflammation. Also, it highlights the efficacy and tolerability of abatacept as a targeted therapy for neuroinflammation in CTLA4-d.