49, XXXXX
| 49, XXXXX | |
|---|---|
| Classification and external resources | |
| Specialty | Lua error in Module:Wikidata at line 446: attempt to index field 'wikibase' (a nil value). |
| ICD-10 | Q97.1 |
| DiseasesDB | 32625 |
| Patient UK | 49, XXXXX |
XXXXX syndrome (also called pentasomy X or 49,XXXXX) is a type of aneuploidy (an abnormal number of chromosomes) which results in the presence of three additional X chromosomes. The condition was first described in 1963.[1] It is characterized by severe intellectual disability, short stature and abnormalities to the head and face.[1] As these features can be seen in other conditions, karyotyping must be carried out to confirm diagnosis. There have been cases of XXXXX syndrome being misdiagnosed as Down syndrome.[1][2]
It is an extremely rare condition with no more than 30 patients reported in medical literature.[3] The exact incidence is not known but it may be similar to the rate of 1 in 85,000 seen in males with 49, XXXXY syndrome.[3][4]
Signs and symptoms
The main characteristics of XXXXX syndrome are intellectual disability, short stature and craniofacial abnormalities.[1] Other physical traits include the following:
- Small head[5]
- Ear abnormalities[5]
- Widely spaced eyes with upward slanting palpebral fissures and epicanthal folds [5]
- Short neck[5]
- Broad nose with a depressed nasal bridge[1]
- Hyperextension of the elbows[1][5]
- Dental abnormalities and cleft palate[1][5]
- Clinodactyly of the 5th finger[1][5]
- Deformities of the feet[1][5]
- Heart defects[3][5]
Causes
The aneuplody 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.[1][3] 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.[3]
See also
References
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