XKR3 is an X-chr22-located gene belonging to the XK family of putative membrane transporters 1. Unlike the ubiquitously expressed XK protein, XKR3 shows tissue-restricted expression patterns and shares structural homology with XK family members, including predicted transmembrane topology 1. XKR3 has emerged as a genetic risk factor for pituitary adenoma associated with vestibular schwannoma (PAVS). Germline XKR3 mutations were identified in 2 of 4 PAVS patients, suggesting XKR3 as a genetic predisposition factor for this tumor combination, which showed significant association with older age at presentation 2. Additionally, XKR3 was identified as a genome-wide association study (GWAS) locus significantly associated with Alzheimer's disease endophenotypes, including amyloid-β, tau, and neurodegeneration biomarkers 3. In reproductive biology, XKR3 was identified as a signature gene with low expression in non-obstructive azoospermia (NOA) patient testis samples, with localization to spermatids and potential involvement in spermatogenesis regulation 4. XKR3 was also identified among genes with elevated mutation rates in carotid paragangliomas, suggesting involvement in neuroendocrine tumor pathogenesis 5. These findings suggest XKR3 participates in multiple disease processes, though its precise molecular function remains to be defined.