FTHL17 (ferritin heavy chain like 17) is an X-linked gene encoding a ferritin-like protein with distinct properties from canonical ferritins. Unlike traditional ferritins, FTHL17 produces a 24-mer ferritin protein lacking ferroxidase activity and displaying reduced physical stability 1. The protein shows partial nuclear localization rather than exclusive cytoplasmic distribution, suggesting functions beyond iron storage 1. FTHL17 is normally expressed in spermatogonia and early embryonic cells, with testis-specific expression relevant to male reproductive function 2. Clinically, FTHL17 mutations have been associated with 46,XY pure gonadal dysgenesis (PGD), with a novel c.GA442_443TT (p.E148L) mutation identified in a Chinese pedigree exhibiting 100% prevalence of gonadal tumors and X-linked recessive inheritance 3. In vitro studies demonstrated that FTHL17 perturbation decreases protein expression and cell proliferation, suggesting involvement in the testis-determining pathway and tumorigenesis 3. Additionally, FTHL17 has been identified as a cancer-germline gene activated in various tumor types including colorectal adenomas and head and neck squamous cell carcinoma, with potential expression as a tumor-associated antigen 45. FTHL17 maintains cell-type-specific X-inactivation patterns despite overall X-chromosome X abnormalities in certain conditions 6.