KCTD16 (potassium channel tetramerization domain containing 16) functions as an auxiliary subunit of GABA-B receptors that modulates receptor pharmacology and kinetics. Structurally, KCTD16 forms an open pentameric oligomerization domain that directly binds to the GABAB2 receptor C-terminus, with specific interfacial residues conserved among KCTD family members 1. This interaction increases agonist potency and alters G-protein signaling by accelerating onset and promoting desensitization. KCTD16 is implicated in nervous system development and neurodevelopmental disorders; genome-wide analysis identified KCTD16 as a candidate gene in autism spectrum disorder 2. Clinically, KCTD16 autoantibodies serve as a critical paraneoplastic marker. In anti-GABABR encephalitis, KCTD16 antibodies are present in 95% of paraneoplastic cases versus 33% of non-paraneoplastic cases 3, strongly correlating with underlying small-cell lung carcinoma 4. Patients with paraneoplastic anti-GABABR disease and KCTD16 antibodies present with severe seizures, cognitive impairment, and behavioral changes 3. Notably, nonparaneoplastic GABABR-encephalitis patients rarely have KCTD16 antibodies (6%) and show better neurological outcomes than paraneoplastic cases 5, highlighting KCTD16's role in tumor immune tolerance breakdown.