FAM13C1 (family with sequence similarity 13, member C), also known as FAM13C, is a 585 amino acid protein that belongs to the FAM13 family. Existing as three alternatively spliced isoforms, the gene encoding FAM13C1 maps to human chromosome 10, which contains over 800 genes, 135 million nucleotides and makes up nearly 4.5% of the human genome. PTEN is an important tumor suppressor gene located on chromosome 10 and, when defective, causes a genetic predisposition to cancer development known as Cowden syndrome. The chromosome 10 encoded gene ERCC6 is important for DNA repair and is linked to Cockayne syndrome which is characterized by extreme photosensitivity and premature aging. Tetrahydrobiopterin deficiency and a number of syndromes involving defective skull and facial bone fusion are also linked to chromosome 10. As with most trisomies, trisomy 10 is rare and is deleterious.