Pentasomy X

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Pentasomy X[edit | edit source]

Pentasomy X
Synonyms 49,XXXXX, penta X, XXXXX syndrome[1]
Pronounce
Field
Symptoms Intellectual disability, short height, low-set ears, decreased muscle tone, developmental delay[1][2]
Complications Congenital heart disease[3]
Onset
Duration
Types
Causes 5 X chromosomes[2]
Risks Older parents[2]
Diagnosis Chromosomal analysis[2]
Differential diagnosis Down syndrome, triple X syndrome, tetrasomy X, Turner syndrome[2]
Prevention
Treatment Based on symptoms[2]
Medication
Prognosis
Frequency Extremely rare[2]
Deaths


Pentasomy X, also known as 49,XXXXX, is a chromosomal abnormality in which a female has five X chromosomes instead of the normal two.[2] Signs may include intellectual disability, short height, low-set ears, decreased muscle tone, and developmental delay.[1][2] Complications may include congenital heart disease.[3]

The condition is due to problems during the formation of the reproductive cells in a person's parents.[2] Risk factors include older parents at the time of conception.[2] Diagnosis is suspected based on symptoms and confirmed by chromosomal analysis.[2]

Treatment is based on symptoms.[2] The condition is extremely rare, with less than forty reported cases as of 2011.[2][3] The condition was first described in 1963.[2]

Signs and symptoms[edit | edit source]

The main characteristics of pentasomy X are intellectual disability, short stature and craniofacial abnormalities.[4] Other physical traits include the following:

Foetal karyotype demonstrating pentasomy X

Causes[edit | edit source]

The aneuploidy is thought to be caused by problems occurring during meiosis, either in the mother or in both the mother and father. Successive nondisjunctions have been observed in the mother of at least one patient.[4][6]

The features of the syndrome likely arise due to failure of X-inactivation and the presence of multiple X chromosomes from the same parent causing problems with parental imprinting. In theory, X-inactivation should occur and leave only one X chromosome active in each cell. However, failure of this process has been observed in one individual studied. The reason for this is thought to be the presence of an unusually large, and imbalanced, number of X chromosomes interfering with the process.[6]

See also[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 1.2 "49,XXXXX syndrome". GARD. Retrieved 22 January 2018.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 "Penta X Syndrome". NORD (National Organization for Rare Disorders). 2003. Retrieved 22 January 2018.
  3. 3.0 3.1 3.2
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8
  6. 6.0 6.1 6.2

External links[edit | edit source]

Classification
  • ICD-10: Q97.1
External resources
  • Orphanet: 11


Pentasomy X Resources
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