Overview: What every practitioner needs to knowAre you sure your patient has fragile X syndrome? What are the typical findings for this disease? Fragile X syndrome (FXS) is the most common inherited disorder causing mental retardation. It results from a trinucleotide repeat expansion on the X chromosome. As an X-linked condition, affected male individuals (who…
OVERVIEW: What every practitioner needs to knowAre you sure your patient has Klinefelter syndrome? What are the typical findings for this disease? Klinefelter syndrome is characterized by the presence of an extra (one or more) X chromosome in male individuals, giving a 47,XXY rather than 46,XY karyotype. Klinefelter syndrome occurs in 1/500-1000 live births and…
OVERVIEW: What every practitioner needs to know Are you sure your patient has Turner syndrome? What are the typical findings for this disease? Turner syndrome (TS) is caused by the absence of the short arm of one X chromosome in a female in every cell of the body. The most common karyotype in TS is…
OVERVIEW: What every practitioner needs to know Trisomy 13, caused by the presence of an extra chromosome 13 in every cell of the body, is the most rare and severe of the viable trisomic conditions. Mean survival is less than 1 week of age owing to cardiac or pulmonary complications, congenital heart defects, or severe…
OVERVIEW: What every practitioner needs to know Are you sure your patient has trisomy 21? What are the typical findings for this disease? Trisomy 21, or Down syndrome, is the most common cause of intellectual disability. Resulting from an extra copy of chromosome 21 in every cell of the body, it is also the most…
OVERVIEW: What every practitioner needs to know Trisomy 18, caused by having 3 copies of chromosome 18 rather than the typical 2 copies, is the second most common chromosome abnormality in live births following trisomy 21, or Down syndrome. Trisomy 18 is a severe condition leading to severe to profound intellectual disability, pre- and postnatal…
