KCTD1 (potassium channel tetramerisation domain containing 1), also known as C18orf5, is a 257 amino acid protein that contains one BTB domain, suggesting an involvement in transcriptional control. The gene encoding KCTD1 maps to human chromosome 18, which houses over 300 protein-coding genes and contains nearly 76 million bases. There are a variety of diseases associated with defects in chromosome 18-localized genes, some of which include Trisomy 18 (also known as Edwards syndrome), Niemann-Pick disease, hereditary hemorrhagic telangiectasia, erythropoietic protoporphyria and follicular lymphomas.