Common Chromosomal Defects
Related Subjects:
| Osteoporosis
| Autosomal Dominant
| Autosomal Recessive
| X Linked Recessive
|Dementias
|Chromosomal Defects
|Turner's syndrome (Children)
|Down's syndrome (Children)
⬇️ Down Syndrome (Trisomy 21)
- Genetic: Extra chromosome 21
- Incidence: ~1 in 700 births
- Key Features: Intellectual disability 🧠, hypotonia, characteristic facies 🙂, congenital heart disease ❤️
- Additional: ↑ risk of acute leukemia, early-onset Alzheimer disease
♀️ Turner Syndrome (45, X0)
- Genetic: Monosomy X (missing one X chromosome)
- Incidence: ~1 in 2500 female births
- Key Features: Short stature 📏, webbed neck, streak ovaries → infertility, cardiovascular anomalies ❤️
- Additional: Phenotypic females only, may need estrogen therapy
♂️ Klinefelter Syndrome (47, XXY)
- Genetic: Extra X chromosome (XXY)
- Incidence: ~1 in 650 male births
- Key Features: Tall stature 📏, hypogonadism, infertility, learning difficulties, gynecomastia
- Additional: Often undiagnosed until puberty, testosterone replacement may help
🎵 Williams Syndrome (7q11.23 Deletion)
- Genetic: Deletion at 7q11.23
- Incidence: ~1 in 10,000 births
- Key Features: “Elfin” facies 🧚, intellectual disability, hypercalcemia, cardiovascular issues ❤️
- Additional: “Cocktail party” personality 🍸, verbal skills stronger than visuospatial
😄 Angelman Syndrome
- Genetic: Maternal deletion at 15q11-q13
- Incidence: ~1 in 12,000–20,000 births
- Key Features: Severe intellectual disability 🧠, ataxia 🚶, seizures ⚡, frequent laughter 😂
- Additional: Historic term “happy puppet syndrome”, profound speech impairment
🍽️ Prader-Willi Syndrome
- Genetic: Paternal deletion at 15q11-q13
- Incidence: ~1 in 10,000–30,000 births
- Key Features: Neonatal hypotonia 🍼, hyperphagia 🍔 → obesity, short stature 📏, small hands/feet
- Additional: ↑ risk of type 2 diabetes, behavioural issues common
🧩 DiGeorge Syndrome (22q11.2 Deletion)
- Genetic: Deletion at 22q11.2
- Incidence: ~1 in 4000 births
- Key Features: Congenital heart defects ❤️, cleft palate 👄, thymic aplasia 🦠 → immunodeficiency, hypocalcemia
- Additional: Also called “22q11.2 deletion syndrome”, T-cell deficiency possible
👶 Edwards Syndrome (Trisomy 18)
- Genetic: Extra chromosome 18
- Incidence: ~1 in 6000 births
- Key Features: Severe intellectual disability 🧠, clenched hands ✊, rocker-bottom feet 👣, congenital heart disease ❤️
- Additional: High infant mortality, micrognathia, low-set ears
👶 Patau Syndrome (Trisomy 13)
- Genetic: Extra chromosome 13
- Incidence: ~1 in 10,000 births
- Key Features: Severe intellectual disability 🧠, polydactyly 🖐️, holoprosencephaly, cleft lip/palate 👄
- Additional: Often fatal in early infancy, congenital heart defects common
