Background: The product of this gene belongs to the family of classical tyrosine-specific protein tyrosine phosphatases. Many protein tyrosine phosphatases have been shown to regulate fundamental cellular processes and several are mutated in human diseases. Chromosome 10q contains a segmental duplication resulting in multiple copies of the protein tyrosine phosphatase, non-receptor type 20 gene. The two nearly identical copies are designated as PTPN20A and PTPN20B. A third copy is only partially duplicated and contains a pseudogene, designated as PTPN20C. This gene encodes the more telomeric copy, PTPN20B. Multiple alternatively spliced transcript variants encoding different isoforms have been identified.