ABSTRACT
Anomalies of the X and Y chromosomes form a significant part of the total load of chromosome mutations carried by the human species. The eponym Turner syndrome was coined to describe a new syndrome of sexual infantilism, webbing of the neck, short stature, and cubitus valgus first described by Turner in 1938. The phenotype of patients with a ring X chromosome may be either severe or mild, depending on whether or not the ring contains the XIST locus and can be inactivated. Klinefelter et al. described a syndrome in nine male patients who had gynecomastia, hypogonadism with hyalinized seminiferous tubules and absent spermatogenesis, but with intact Leydig cells. Behavioral problems and learning difficulties often, but not always, accompanied by a lower IQ need to be recognized and treated by appropriate remedial action and assistance in school. Sex chromosome anomalies are perhaps the most common form of chromosome anomaly detected in clinical practice.
