Coexistence of Autoimmune Antibody-Nmda and Paraneoplastic Antibody Anti-Hu in a Patient with Behavioral, Sensory, Motor, Cerebellar and Extrapyramidal Features – A Rare Case Report

N-Methyl-d-aspartate receptor (NMDAR) antibody encephalitis is an autoimmune syndrome in which antibody is produced against the NMDAR. The syndrome is frequently associated with ovarian teratomas. Clinical features include auditory and visual hallucinations, delusions, behavioral change, impaired consciousness, motor disturbance (ranging from dyskinesia to catatonia), seizures, and autonomic dysfunction. Anti-Hu is a paraneoplastic antibody which binds to tumors and neural cells. Clinical features include sensory neuropathy, cerebellar ataxia, limbic encephalitis, brainstem encephalitis and is commonly associated with small-cell lung carcinomas. A 58 year old male presented with history of gradually progressive behavior disturbance, sensory loss in lower limbs, tremulousness of all four limbs, weakness which started in proximal limbs, intermittent involuntary posturing of left upper limb and neck for 3 months, recent onset swallowing difficulty. On examination had behavior disturbance, lower motor neuron type of quadriparesis, sensory ataxia, asymmetrical cerebellar signs, left upper limb and neck dystonia with ninth and tenth cranial nerve involvement. Hematological investigations- normal, ANA-negative, serum and urine protein electrophoresis normal. CEMRI brain and cord –normal, PET-CT-normal, nerve conduction studies showed pure sensory axonal neuropathy, EMG-fasciculations in deltoid and first dorsal interossei. Autoimmune panel-NMDA antibody positive. Paraneoplastic panel-anti Hu antibody positive. Till date the simultaneous coexistence of autoimmune antibody-NMDA and paraneoplastic antibody-anti Hu has been described very rarely, moreover both behavior disturbance and cerebellar involvement which is in common presenting features NMDA and anti-Hu antibodies respectively with some atypical features like cranial nerve involvement are present in the patient which further make this case unique.