Retrospective study done in a tertiary care teaching hospital in South India from 2013-2023. Patients aged 18 years or above included in the study if serum or CSF tested positive for CASPR 2 antibodies in cell based assay. Those with additional antibody positive were excluded.

There were 22 patients (15 males,mean age 61.4545 [+] years,standard deviation-SD 14.689) with CASPR 2 antibody positive, 8  presented with CNS involvement (encephalopathy, behavioural abnormalities, seizures and dysautonomia, 14 with peripheral nervous system symptoms (parasthesias, muscle twitchings and cramps).Seven (31.81%) had renal manifestation as new onset proteinuria - heavy proteinuria -1, moderate proteinuria -2,  mild proteinuria in 4  after excluding all other causes. One patient underwent renal biopsy which showed of membranous nephropahy. Proteinuria improved with immunotherapy in all the seven patients. Five patients received rituximab therapy preceded by IV Methyl prednisolone (IVMP) and two of them received additional doses of IVIg(IV Immunoglobulins) also. One received IVMP, oral steroids with Injection cyclophosphamide  and later azathioprine and then other patient received only IVMP and oral steroids.

Proteinuria is the common renal manifestation CASPR2 antibody associated neurological disease. Improvement with immunotherapy indicates a possible autoimmune pathogenesis involving glomeruli. Further studies are required to delineate the exact mechanism underlying this association.