Down Syndrome (Trisomy 21)
Down syndrome, which results from an extra copy of chromosome 21, is the most common cause of mild to moderate intellectual disability in newborns. Physically, this condition is associated with issues such as heart or other organ defects and impaired hearing or vision. Delayed cognitive development and behavioral problems are also observed in affected individuals. The average life expectancy can reach the 60s, but the various health issues usually lower that value. There is a 30% miscarriage rate associated with trisomy 21. Around 1:600 babies are born with Down syndrome, with the incidence rate increasing with maternal age. There is no cure, but wide varieties of treatments are available and can be customized to each individual’s needs.
Edwards Syndrome (Trisomy 18)
Edwards syndrome, which results from an extra copy of chromosome 18, leads to severe health issues in newborns. Physically, affected individuals have a cleft lip or a cleft palate. Severe organ defects, especially of the heart, brain, and kidneys are also associated with this particular trisomy. There is a high rate of miscarriage for mothers carrying embryos with this chromosomal condition, and any babies that do make it to term usually pass within a year. Any surviving infants have severe intellectual disability along with the organ issues. Unlike Down syndrome, the complications of this condition are harder to manage. The occurrence of this chromosomal abnormality is 1 in 2,500 pregnancies, but due to miscarriages or still births, this rate lowers to 1 in 6,000 live births. There is also a 3:1 female to male predominance.
Patau Syndrome (Trisomy 13)
Patau syndrome, which results from an extra copy of chromosome 13, leads to severe intellectual disabilities and heart problems in those affected. Physically, newborns with trisomy 13 have telling physical traits such as a cleft lip or palate, and extra fingers or toes. Newborns with Patau syndrome usually do not survive past the first year. The incidence rate of Trisomy 13 is about 1 in 5,000 to 15,000 live births each year worldwide.
Turner Syndrome (XO)
Turner syndrome, also known as monosomy X, is a sex chromosome disorder that affects only females. Physically, affected females experience problems in puberty with slow growth and have a short stature. Most also have fertility defects in the form of premature ovarian failure. Although verbal skills are relatively unaffected, skills that involve math, memory, or fine motor are weakened. Other developmental disabilities vary widely within the population of affected females. The incidence rate is estimated to be about 1 in 2,500, though this chromosome defect typically leads to miscarriages or stillbirths. Hormone therapies are the main form of treatment and management for those with Turner syndrome. Those affected usually reach 50 years of age, and life span is reduced by an average of 13 years.
Klinefelter syndrome (XXY)
Klinefelter syndrome is a sex chromosome disorder that affects males. Those affected have learning and behavior problems. Associated physical characteristics do not emerge until puberty, and include being taller than average and having less facial and body hair growth due to low testosterone levels. Affected individuals are more susceptible to osteoporosis and type 2 diabetes, and are infertile due to low testosterone levels. The incidence rate is estimated to be about 1 in 500 to 1,000. Although hormone treatment is available, most affected individuals do not receive any sort of treatment for this disorder, and can live to nearly the same age as healthy individuals. Life expectancy for these individuals is normal.
Triple X (XXX)
Triple X syndrome, also known as trisomy X, is a sex chromosome disorder that affects females. The symptoms of this disorder are milder compared to other chromosomal abnormalities. Physically, affected females do not show a lot of unusual features, except for usually being taller than average. Sexual development is normal, though cognitive and behavioral development may be impacted. Delayed development of language is the most common feature, while delayed development of motor and emotional skills is possible but not as prevalent. About 10% of those affected experience seizures or kidney problems. The incidence rate is estimated to be about 1 in 800 to 1,000.
Jacob syndrome (XYY)
Jacob syndrome is a sex chromosome disorder that affects males. This syndrome is similar to Triple X in females: affected males are typically taller than average, but otherwise show no other physical birth defects. Sexual development is normal, but there is an increased risk for learning disabilities, especially with language. Behavioral problems are also possible, and a small percentage of those affected are also diagnosed with ASD (affected social skills). The incidence rate is estimated to be about 1 in 650 to 1,000. Life expectancy is normal.