Down syndrome trivia: 95 unknown facts about this genetic disorder!

Down syndrome is one of the most common genetic disorders and one that we, as a general public, know so little about!

It is the perfect time to find out more things about it!

1. Down syndrome is also known as trisomy 21
2. It is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21
3. It is typically associated with physical growth delays
4. Mild to moderate intellectual disability
5. And characteristic facial features
6. The average IQ of a young adult with Down syndrome is 50
7. Equivalent to the mental ability of an 8- or 9-year-old child
8. But this can vary widely
9. The parents of the affected individual are typically genetically normal
10. The probability increases from less than 0.1% in 20-year-old mothers to 3% in those of age 45
11. The extra chromosome is believed to occur by chance
12. With no known behavioral activity or environmental factor that changes the probability
13. Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing
14. Or after birth by direct observation and genetic testing
15. Since the introduction of screening, pregnancies with the diagnosis are often terminated
16. Regular screening for health problems common in Down syndrome is recommended throughout the person’s life
17. There is no cure for Down syndrome
18. Education and proper care have been shown to improve quality of life
19. Some children with Down syndrome are educated in typical school classes
20. While others require more specialized education
21. Some individuals with Down syndrome graduate from high school
22. And a few attend post-secondary education
23. In adulthood, about 20% in the United States do paid work in some capacity
24. With many requiring a sheltered work environment
25. Support in financial and legal matters is often needed
26. Life expectancy is around 50 to 60 years in the developed world with proper health care
27. Down syndrome is one of the most common chromosome abnormalities in humans
28. It occurs in about one per 1,000 babies born each year
29. In 2015, Down syndrome was present in 5.4 million individuals globally
30. And resulted in 27,000 deaths
31. Down from 43,000 deaths in 1990
32. It is named after John Langdon Down
33. A British doctor who fully described the syndrome in 1866
34. Some aspects of the condition were described earlier by Jean-Étienne Dominique Esquirol in 1838 and Édouard Séguin in 1844
35. In 1959, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered
36. Those with Down syndrome nearly always have physical and intellectual disabilities
37. As adults, their mental abilities are typically similar to those of an 8- or 9-year-old
38. They also typically have poor immune function
39. And generally reach developmental milestones at a later age
40. They have an increased risk of a number of other health problems
41. Including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders
42. People with Down syndrome may have some or all of these physical characteristics
43. A small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue
44. These airway changes lead to obstructive sleep apnea in around half of those with Down syndrome
45. Other common features include: a flat and wide face, a short neck, excessive joint flexibility, extra space between big toe and second toe, abnormal patterns on the fingertips and short fingers
46. Instability of the atlantoaxial joint occurs in about 20% and may lead to spinal cord injury in 1- 2%
47. Hip dislocations may occur without trauma in up to a third of people with Down syndrome
48. Growth in height is slower, resulting in adults who tend to have short stature
49. The average height for men is 154 cm (5 ft 1 in) and for women is 142 cm (4 ft 8 in)
50. Individuals with Down syndrome are at increased risk for obesity as they age
51. Growth charts have been developed specifically for children with Down syndrome
52. This syndrome causes about a third of cases of intellectual disability
53. Many developmental milestones are delayed with the ability to crawl typically occurring around 8 months rather than 5 months
54. And the ability to walk independently typically occurring around 21 months rather than 14 months
55. Most individuals with Down syndrome have mild or moderate intellectual disability
56. With some cases having severe difficulties
57. Those with mosaic Down syndrome typically have IQ scores 10- 30 points higher
58. As they age, people with Down syndrome typically perform worse than their same-age peers
59. Commonly, individuals with Down syndrome have better language understanding than ability to speak
60. Between 10 and 45% have either a stutter or rapid and irregular speech
61. Making it difficult to understand them
62. Some after 30 years of age may lose their ability to speak
63. They typically do fairly well with social skills
64. Behavior problems are not generally as great an issue as in other syndromes associated with intellectual disability
65. In children with Down syndrome, mental illness occurs in nearly 30% with autism occurring in 5- 10%
66. People with Down syndrome experience a wide range of emotions
67. While people with Down syndrome are generally happy
68. Symptoms of depression and anxiety may develop in early adulthood
69. Children and adults with Down syndrome are at increased risk of epileptic seizures
70. Which occur in 5- 10% of children and up to 50% of adults
71. This includes an increased risk of a specific type of seizure called infantile spasms
72. Many (15%) who live 40 years or longer develop Alzheimer disease
73. In those who reach 60 years of age, 50- 70% have the disease
74. Hearing and vision disorders occur in more than half of people with Down syndrome
75. Vision problems occur in 38 to 80%
76. Between 20 and 50% have strabismus, in which the two eyes do not move together
77. Cataracts occur in 15%
78. And may be present at birth
79. Keratoconus (a thin, cone-shaped cornea) and glaucoma (increased eye pressure) are also more common
80. As are refractive errors requiring glasses or contacts
81. Brushfield spots (small white or grayish/brown spots on the outer part of the iris) are present in 38 to 85% of individuals
82. Hearing problems are found in 50–90% of children with Down syndrome
83. This is often the result of otitis media with effusion which occurs in 50–70%
84. And chronic ear infections which occur in 40 to 60%
85. Down syndrome is caused by having three copies of the genes on chromosome 21
86. Rather than the usual two
87. The parents of the affected individual are typically genetically normal
88. Those who have one child with Down syndrome have about a 1% risk of having a second child with the syndrome
89. If both parents are found to have normal karyotypes
90. The extra chromosome content can arise through several different ways
91. The most common cause is a complete extra copy of chromosome 21, resulting in trisomy 21
92. In 1.0 to 2.5% of cases, some of the cells in the body are normal and others have trisomy 21
93. Known as mosaic Down syndrome
94. The other common mechanisms that can give rise to Down syndrome include: a Robertsonian translocation, isochromosome, or ring chromosome
95. These contain additional material from chromosome 21 and occur in about 2.5% of cases