A Rare Central Nervous System Involvement Due to CTLA-4 Gene Defect.

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) haploinsufficiency is the defect of one of the checkpoint inhibitory molecules and defined as a primary immunodeficiency characterized by immune dysregulation. A 26-year-old female with a history of autoimmune hemolytic anemia, autoimmune thrombocytopenia, and hypogammaglobulinemia was admitted with an inability to walk, urinary hesitancy, and bowel incontinence. Neurological examination revealed mild weakness, pyramidal, and deep sensorial involvement of the left lower extremity. Brain MRI revealed periventricular, juxtacortical, and cerebellar inflammatory lesions. Thoracic spinal MRI showed a longitudinaly extensive cord lesion. Additionally, thoracal CT showed parenchymal opacities and bilateral hilar lymph nodes. The biopsy from mediastinal lymph nodes and lung parenchyma demonstrated a low-grade lymphoproliferation and grade 1 "Lymphomatoid granulomatosis". Detailed laboratory analyses indicated the diagnosis of ''common variable immunodeficiency''. Next-generation sequencing with primary immunodeficiency panel revealed a heterozygous mutation in CTLA-4 (c.436G>A(p.G146R)(p.Gly146Arg)). After molecular diagnosis, abatacept therapy was started as a targeted therapeutic approach with subcutaneous immunoglobulin therapy.