49,XXXXX syndrome
Alternate names[edit | edit source]
Pentasomy X; Chromosome XXXXX syndrome; Penta-X syndrome; Pentasomy X syndrome; Chromosome X pentasomy
Definition[edit | edit source]
Pentasomy X is a sex chromosome anomaly caused by the presence of three extra X chromosomes in females (49,XXXXX instead of 46,XX).
Epidemiology[edit | edit source]
The prevalence is unknown but less than 40 cases have been described in the literature so far.
Cause[edit | edit source]
- Pentasomy X is generally thought to arise as a result of successive maternal nondisjunction during meiosis.
- 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.
Signs and symptoms[edit | edit source]
- Pentasomy X is associated with developmental delays, short stature, craniofacial anomalies and musculoskeletal abnormalities. T
- he craniofacial anomalies may include microcephaly, micrognathia, plagiocephaly, hypertelorism, upslanting palpebral fissures, a flat nasal bridge and ear malformations.
- The hands and feet are generally small and camptodactyly, clinodactyly, and radioulnar synostosis are common findings.
- Immunoglobulin anomalies and an increased susceptibility to infection have also been reported. Cardiovascular malformations may also be present.
- External genitalia are generally normal but gonadal dysfunction has been reported.
- Developmental profiles usually show global developmental delay and intellectual disability; however, receptive language skills are usually less severely affected than expressive language abilities.
Clinical presentation[edit | edit source]
For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.
80%-99% of people have these symptoms
- Low-set, posteriorly rotated ears
- Muscular hypotonia(Low or weak muscle tone)
30%-79% of people have these symptoms
- Camptodactyly of finger(Permanent flexion of the finger)
- Clinodactyly of the 5th finger(Permanent curving of the pinkie finger)
- Global developmental delay
- Hypertelorism(Wide-set eyes)
- Intellectual disability(Mental deficiency)
- Microcephaly(Abnormally small skull)
- Micrognathia(Little lower jaw)
- Plagiocephaly(Flat head syndrome)
- Radioulnar synostosis(Fused forearm bones)
- Short foot(Short feet)
- Short stature(Decreased body height)
- Small hand(Disproportionately small hands)
- Strabismus(Cross-eyed)
- Upslanted palpebral fissure(Upward slanting of the opening between the eyelids)
- Wide nasal bridge(Broad nasal bridge)
5%-29% of people have these symptoms
- Abnormal cardiac septum morphology
- Abnormality of immune system physiology
- Delayed puberty(Delayed pubertal development)
- Hip dysplasia
- Patent ductus arteriosus
Diagnosis[edit | edit source]
Diagnosis is suspected based on symptoms and confirmed by chromosomal analysis.
Treatment[edit | edit source]
Treatment is based on symptoms.
NIH genetic and rare disease info[edit source]
49,XXXXX syndrome is a rare disease.
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