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. Most people with pentasomy X and heart issues do not need surgery to help them, but a small amount do. Some people with the disorder may also have kidney and urinary problems.

Some comorbidities (disorders that one has alongside their main disorder) that people with pentasomy X may have are cerebral palsy and Dandy-Walker malformation. These conditions affect the brain.

### 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. There is no known case where a woman with pentasomy X had kids. Fertility is not as high, but some people with the disorder might be able to have kids.

### 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. The cognitive capacity (mental state) of adults with pentasomy X resembles six to eight-year-olds. People with pentasomy X often need support and help to have basic living and job skills. 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. They are often described as being shy and cooperative.

## Causes

Pentasomy is caused by nondisjunction. This is when an egg or sperm makes too many or too little chromosomes. It happens during meiosis. People with pentasomy X inherit extra chromosomes from their mother. Whether the age of the mother affects the chance of having pentasomy X is not known. 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). For example, some parents may think their child has Down syndrome before they are diagnosed with pentasomy X because they have similar symptoms.

## Prognosis

The long-term prognosis (how a disorder will affect someone over time) is not fully known because of how rare it is. Some studies say the prognosis is bad because people with the disorder have symptoms for their whole life. Some support groups say that adults with pentasomy X can have good health. The severity of pentasomy X can vary, but people with it often need support and help for their whole life. There have been reports of women with pentasomy X who could have part-time jobs. Prognosis is usually good if the person with pentasomy X has strong support from their parents, caregivers, or other people.

## Prevalence

Pentasomy X is very rare. One estimate says that 1 in 85,000 females have the condition. This is similar to the prevalence of XXXXY syndrome, a similar disorder in males. 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.

## History

Pentasomy X was first diagnosed in 1963 when a two-year-old girl had a karyotype of her done because she had severe intellectual disability. 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.

## Infobox (medical condition)

- **name**: Pentasomy X
- **synonym**: Penta-X, XXXXX syndrome, 49,XXXXX syndrome
- **image**: Pentasomy X phenotype.png
- **alt**: 15-year-old girl with common skeletal, limb, and facial features in pentasomy X
- **caption**: 15-year-old girl with common skeletal, limb, and facial features in pentasomy X
- **specialty**: Medical genetics
- **symptoms**: Intellectual disability, physical defects, heart issues
- **onset**: Prenatal
- **duration**: Lifelong
- **causes**: Nondisjunction
- **frequency**: 1 in 85,000 to 250,000