Primary Adrenal Insufficiency in a Patient with Mosaic Klinefelter Syndrome.

Klinefelter syndrome (KS) is a common sex chromosome disorder characterized by hypergonadotropic hypogonadism. Primary adrenal insufficiency (PAI) has rarely been reported in association with KS, particularly in mosaic cases. We report a case involving a 39-year-old man with mosaic KS (47,XXY/46,XY) and PAI. He presented with hyperkalemia and subtle clinical features without hypotension. Endocrinological evaluation confirmed PAI, and elevated gonadotropin levels with low testosterone levels indicated primary hypogonadism. Steroid profiling using liquid chromatography-tandem mass spectrometry showed reduced testosterone and dihydrotestosterone levels with preserved androgen precursors. This case illustrates the rare coexistence of PAI and mosaic KS.