Disorders of Prenatal Development

Question 1

Prader-Willi Syndrome

Answer 1

Cause: deletion on the paternal chromosome 15

Symptoms: almond-shaped eyes, narrow forehead, short stature and small hands and feet; hypotonia (poor muscle tone); global developmental delays; intellectual disabilities; hyperphagia (chronic overeating) and obesity; hypogonadism; and skin-picking and other self-injurious behaviors.

Question 2

Angelman Syndrome

Answer 2

Cause: deletion on maternal chromosome 15

Symptoms: microcephaly (small head and brain); a wide jaw and pointed chin; severe developmental delays; communication and intellectual disabilities; hyperactivity, a tendency to be unnaturally happy; ataxia; seizures; and hand-flapping.

Question 3

Cri-du-chat Syndrome

Answer 3

Cause: deletion on chromosome 5

Symptoms: high-pitched (cat-like) cry, intellectual disability, developmental delays, microcephaly, low birth weight, weak muscle tone, and characteristic facial features (e.g., widely set eyes, low-set ears, round face).

Question 4

Klinefelter Syndrome

Answer 4

Cause: affects males due to the presence of two or more X chromosomes in addition to a single Y chromosome.

Symptoms: Males with this disorder develop a normal male identity but have incomplete development of secondary sex characteristics, gynecomastia (breast enlargement), and a low testosterone level. They also have disproportionately long arms and legs and are taller than normal and may have delays in language development, learning disabilities, and impaired problem-solving and social skills.

Question 5

Turner Syndome

Answer 5

Cause: affects females due to all or part of an X chromosome missing.

Symptoms: Females with this disorder don’t develop secondary sex characteristics and are infertile, and they have a short stature, stubby fingers, drooping eyelids, a receding or small lower jaw, and a web-like neck. They may also have learning disabilities, vision and hearing problems, skeletal abnormalities, heart defects, and kidney and urinary tract abnormalities.

Question 6

Down Syndrome

Answer 6

Cause: autosomal Disorder either caused by trisomy 21 (most common), mosaic trisomy 21, or translocation trisomy 21.

Symptoms: a wide face, thick tongue, and almond-shaped eyes; developmental delays; intellectual disability (usually mild to moderate); hypotonia (decreased muscle tone); a short stocky build; and an elevated risk for vision and hearing problems, heart defects, hypothyroidism, and Alzheimer’s disease.

Question 7

Fragile X Syndrome (FXS)

Answer 7

Cause: genetic disorder caused by changes in a gene called Fragile X Messenger Ribonucleoprotein 1 (FMR1). FMR1 usually makes a protein that is needed for brain development. People who have FXS do not make this protein.

Symptoms: developmental delays; learning disabilities; and
social and behavior problems (such as not making eye contact, anxiety, trouble paying attention, hand flapping, acting and speaking without thinking, and being very active).