A tall man with gynecomastia and testicular atrophy has a testicular biopsy that shows sparse, completely hyalinized seminiferous tubules with a complete absence of germ cells and only rare Seoli cells. Leydig cells are present in large clumps between the hyalinized tubules. Which of the following genetic disorders should be suspected?

The testicular changes described are those observed in Klinefelter's syndrome, most often due to 47, XXY genetics. Testicular feminization syndrome is due to a genetically determined unresponsiveness to testosterone that produces a phenotypic female in an individual with 46, XY chromosomes. Trisomy 18 is Edwards' syndrome, characterized by facial features that are small and delicate. Trisomy 21 is Down syndrome, the most common trisomy. Characteristics include oblique palpebral fissures, epicanthal folds, endocardial cushion defects, simian creases, and high-arched palate, among other anomalies. Ref: Wyatt C., Butterwoh IV J.F., Moos P.J., Mackey D.C., Brown T.G. (2008). Chapter 6. Genetic Disorders. In C. Wyatt, J.F. Butterwoh IV, P.J. Moos, D.C. Mackey, T.G. Brown (Eds), Pathology: The Big Picture.