Developmentally, tetrasomy X patients frequently show mild delays in the areas of speech development and articulation, language expression and understanding, and reading skills.

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This condition occurs only in females, as there are no Y chromosomes present.

Tetrasomy X was first described in 1961, and since then approximately 100 cases have been reported worldwide.

Approximately 60 females have been described in medical literature with this condition.

The majority have also been reported as being longer and taller.

Many also show joint and muscle tone abnormalities, including hypotonia and joint looseness in the hips.

Skeletal problems may also be present, including abnormal curvatures of the spine.An informal study conducted by Tetrasomy & Pentasomy X Syndrome Information and Support found that 10% of girls had joint laxity in the hips and 20% had joint limitations in a sample size of 20 tetrasomy and pentasomy patients.Tetrasomy X is a chromosomal aneuploidy, meaning it arises from a defect in meiosis.This can occur when homologous X chromosomes fail to separate in the formation of the egg or sperm.Tetrasomy X is usually suspected based on symptoms present in the individual and is confirmed via karyotyping, which reveals the extra X chromosomes.Symptoms of tetrasomy X are highly variable, ranging from relatively mild to severe. Physically, tetrasomy X patients tend to have distinctive facial features such as epicanthal folds, flat nasal bridges, upslanting palpebral fissures, midface hypoplasia, small mouths, cleft or high arched palates, delayed or absent teeth, or enamel defects.