Morbid Obesity and Psychiatric Disorders Hiding a Sex Aneuploidy: A Case of Late Diagnosis of 48,XXYY Syndrome

48,XXYY syndrome is a rare sex chromosomal aneuploidy, with a prevalence of 1:18,000 - 1:50,000 males. Despite it being considered as a variant of Klinefelter syndrome, it is now known to be a distinct entity, differing from the latter due to a greater degree of severity and prevalence of psychiatric disorders and mental deficiency. We present the case of a 37-year-old man with psychiatric disease who attended our department due to morbid obesity, identified as a 48,XXYY genotype. Clinical evaluation and cytogenetic analysis is presented.