Based on limited published evidence, IGSF23 is an immunoglobulin superfamily member localized to the plasma membrane with predicted roles in cell-cell adhesion. UniProt annotations suggest involvement in osteoclast differentiation. A homozygous loss-of-function mutation (c.295C>T) causing premature truncation was identified in osteopetrosis patients, resulting in impaired osteoclast differentiation from peripheral blood mononuclear cells 1. Mechanistically, IGSF23 deficiency reduced c-Fos and NFATC1 expression via mitogen-activated protein kinase pathway inhibition 1. Additionally, IGSF23 was identified as a tumor mutation burden-related gene associated with disease-free survival in epithelial ovarian cancer 2.