C18orf1 is a 306 amino acid single-pass membrane protein that contains one LDL-receptor class A domain and belongs to the PMEPA1 family. C18orf1 exists as five alternatively spliced isoforms that display selective expression and are encoded by a gene that 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.