TETRAPLOIDY

• A frequently lethal ploidy syndrome marked by the presence of four sets of chromosomes (92,XXYY or 92,XXXX) usually resulting in spontaneous abortions. Infants who survive usually exhibit mental retardation and multiple craniofacial, limb, cardiovascular, renal, and other variable malformations.

Klinefelter Syndrome

• Two or more X chromosomes and one Y, resulting in a phenotypic male

• 1/8000 live male births

• extra X derived maternally in 60% of cases

Symptoms

• Tall, disproportionately long arms and legs

• small, firm testes

• gynecomastia in 33% of cases

• puberty at normal age, light facial hair

• predisposed to LDs

• clinical variation is high- many appear normal physically and intellectually

• Mosaicism occurs in 15% of cases

• sometimes 3,4, even 5 X chromosomes appear along with the Y

• As the number of X chromosomes increases the severity of mental retardation and malformation increases

Diagnosis

• Diagnosis of rare sex chromosome aneuploidies is detected by FISH analysis or by karyotyping to identify duplicate chromosomes.