This document summarizes the medical case of a 27-year-old male patient presenting with sparse facial hair growth and other signs and symptoms. After examinations and tests, the patient was diagnosed with Klinefelter syndrome based on a 47,XXY karyotype. Klinefelter syndrome is a sex chromosome aneuploidy disorder where males are born with an extra X chromosome, leading to reduced testosterone levels and infertility. Long-term testosterone replacement therapy is recommended starting in early adolescence to support normal development.