Klinefelter Syndrome and Turner Syndrome.

Abstract

1. Carole Samango-Sprouse, EdD*,†,‡ 2. Sophia Q. Song, BA‡ 3. Angela E. Lin, MD§ 4. Cynthia M. Powell, MD¶ 5. Andrea L. Gropman, MD*,** 1. *George Washington University, Washington, DC 2. †Florida International University, Miami, FL 3. ‡Department of Research, The Focus Foundation, Davidsonville, MD 4. §Massachusetts General Hospital for Children, Boston, MA 5. ¶University of North Carolina at Chapel Hill, Chapel Hill, NC 6. **Children’s National Medical Center, Washington, DC Sex chromosome aneuploidy (SCA) syndromes refer to disorders with an abnormality of sex chromosome number. The most common are Klinefelter syndrome (KS), resulting from the gain of an X chromosome in males, and Turner syndrome (TS), reflecting the loss of an X chromosome or the presence of a structurally different X chromosome in females. Whereas most patients with KS have nonmosaic 47,XXY, only 40% of women with TS have 45,X; the remainder have a variety of mosaicisms. The syndromes also contrast in that males with KS are characteristically tall, whereas females with TS are typically short unless they receive hormonal treatment. Despite efforts to increase awareness, KS and TS are often underdiagnosed, leading to delayed care. Only 25% of men with KS are ever diagnosed, with fewer than 10% detected prenatally, and with a median age of 27 years for those identified later in life. For TS, the median age at diagnosis is 6.6 years. Although not exclusively, optimal neurocognitive outcomes depend on the timing of diagnosis and access to early targeted treatment, so fortunately the recent development of noninvasive prenatal screening is increasing the early identification of these disorders dramatically. Pediatricians should be aware of signs that allow for early detection, and the importance of prompt referral for testing and therapy. KS occurs in 1 in 660 live births, representing the most common SCA. Affected males have androgen deficiency, which affects endocrine, central nervous system, and neurodevelopmental function. Characteristics include increased height, clinodactyly of the fifth finger, pes planus, and hypogonadism manifesting as …