PTPN2 and systemic lupus erythematosus: The closest paralogue to PTP1B is PTPN2 (also known as TC-PTP) encoded by PTPN2, with shared identity in their catalytic and substrate recognition domains manifesting as a common activity for some substrates.9 Notably, human germline heterozygous and biallelic variants in PTPN2, leading to haploinsufficiency or loss-of-function (LOF) of the encoded protein, have recently been associated with autoimmune enteropathy,10,11 immunodeficiency,12 and systemic autoimmunity including systemic lupus erythematosus and cytopenias.12,13