one extra copy of chromosome 13, resulting in 3 copies of chromosome 13 and 47 total chromosomes. The extra genetic material disrupts the normal course of development.
- it can also be caused by the translocation of a portion of chromosome 13.

- symptoms include: 

congenital heart defects, brain & spinal cord abnormalities, small, poorly developed eyes, extra fingers & toes, cleft lip, decreased muscle tone, microcephaly
- many of these issues are life-threatening. only a very small percent (5-10%) of children live past their first year.

- prevalence:

1 in every 10,000 births in Minnesota

-cause explained:
the extra chromosome presents extra genetic material. this extra information can disrupt the normal course of development, causing the characteristic features of the disorder.

- treatment:

due to the high mortality rate associated with this disorder, surgeries are not always recommended. However, surgeries can help correct some issues if it does not put them at extreme risk.

deletion of part of the long (q) arm on chromosome 18. the missing piece is often near the center of the chromosome. it is an autosomal dominant condition, there only needs to be a deletion in one of the two copies of chromosome 18. it is not inherited, the deletion occurs as a random event during the formation fo the reproductive cells in fetal development.

- symptoms include:

mental retardation, short stature, hypotonia, hearing impairment, foot deformities, tapered digits, wide mouth, microcephaly, palatal defects, short frenulum, carp-like mouth, short palpebral fissures, external ear anomalies, cardiac anomalies.
- most people with this syndrome have delayed skill development. behavioral problems are frequent as well.

- prevalence:

1 in 40,000 live births worldwide

- cause explained:

the partial or complete deletion of the genetic material contained in the long arm of chromosome 18 reduces the amount of growth hormone produced, visions problems with eye movement, reduced thyroid gland activity, and reduced myelin production causing many neurological problems

- treatments:

Surgery to correct craniofacial, skeletal and genital malformations.  congenital heart defects can also be treated by surgery in addition to certain medications. corrective lenses, and surgery can help improve vision. Surgery and specialized hearing aids for hearing impairments. anticonvulsant medications may help control seizures.

the MT-TK gene is the most common cause of MERRF (80% of cases). Along with mutations in the MT-TL1, MT-TH, and MT-TS1 genes in mitochondria

- symptoms include: 

muscle twitches, muscle weakness and progressive stiffness
- the muscle cells appear abnormal when viewing, called ragged red fibers. 

- prevalence:

estimated 1 in 5,000 people worldwide

- cause explained:

reduce the ability of the mitochondria to maintain its normal function including building proteins, using oxygen, and producing energy. The brain and muscles are specifically impacted  due to their high energy requirements.

-treatments:

 Antiseizure medications, levetiracetam for myoclonus, physical therapy, and aerobic exercise. Standard medication is used to treat cardiac symptoms. 

2. Home. (2020, August 10). Retrieved September 26, 2020, from https://rarediseases.org/

3. National Institutes of Health. (n.d.). Retrieved September 26, 2020, from https://www.nih.gov/

4. S. Afr. j. child health vol.9 n.2 Cape Town Jan./Apr. 2015