Pentasomy X

**Pentasomy X**, also known as **penta-X** or **49,XXXXX**, is a rare genetic disorder where a female has five X chromosomes instead of the usual two. About one in 85,000 to 250,000 females have pentasomy X. Because it is so rare, the exact symptoms are not known and they vary. Heart issues, intellectual disability, issues with puberty and the reproductive system, skeleton issues, and a short height are common. Not much is known about pentasomy X due to how rare it is.

## Symptoms 
Because there have been few cases of pentasomy X and the symptoms vary, the exact symptoms that the disorder causes is not fully known. The symptoms of the disorder are similar, and sometimes confused with, Down syndrome or tetrasomy X.

### Physical 
People with pentasomy X are usually shorter than average females. Some physical problems they have can include microcephaly (small head), hypertelorism (wide-spaced eyes), low-set ears, and epicanthal folds (extra skin in the corner of the eyes). Another common problem is severe hypotonia (low muscle tone). This can cause hip dysplasia, where the hip joint is not fully developed. Issues with the teeth is also common. This includes missing teeth and tooth decay. It's also common for the bones in someone with pentasomy X to not be developed correctly. Some people with the disorder also have epilepsy, but this is not common nor severe. Epilepsy in this condition can usually be treated easily.

Heart issues are also common with pentasomy X. About 56.5% of patients with the disorder have some type of heart disorder. Two common heart disorders that people with pentasomy X often have are patent ductus arteriosus and ventricular septal defect.

### Reproductive 
People with pentasomy X go through puberty differently than most women. Some have gone through puberty early while others go through menopause early. The external genitalia (vulva) is usually normal while the internal genitalia (uterus) might not work right and is usually too small. 

### Mental 
Most people with pentasomy X are intellectually disabled. One person with the disorder had a low intelligence, while every other case had an intellectual disability. The average IQ in pentasomy X is 50, around a moderate intellectual disability. Girls with the condition may go to special education classes in regular schools or special schools altogether. People with pentasomy X may have problems communicating and may get frustrated as a result. People with pentasomy X inherit extra chromosomes from their mother. However, in other disorders that are caused by nondisjunction, an older mother increases the chance of getting the disorder.

## Diagnosis 
Pentasomy X is diagnosed through a karyotype. This is when geneticists look through someone's DNA to make a map of their chromosomes. Because the symptoms of pentasomy X is similar to other disorders, it cannot be diagnosed by someone's phenotype (the way their genes make them look). Another estimate says that 1 in 250,000 females have pentasomy X instead. Less than thirty cases of pentasomy X have been found. However, it is assumed that there are many people with it who have not been diagnosed with it. Pentasomy X was one of the last sex chromosome aneuploidies (abnormal amount of cells) to be found. For example, tetrasomy X, where a female has four X chromosomes instead of five like in pentasomy X, was already found in 1961. XXXXY syndrome, a similar condition in males, already had four cases before pentasomy X was found. By 1995, only 25 cases of pentasomy X were found. 

## References