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Trisomy X
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Trisomy X

Trisomy X, also known as 47,XXX, is a chromosomal condition in females characterized by an extra X chromosome in each cell, often resulting in increased height and a higher risk of learning or developmental challenges.

Overview

Trisomy X, or triple X syndrome, occurs when a female has an additional X chromosome in her cells. While many affected females may be taller than average, they typically do not have unusual physical features and usually experience normal sexual development and fertility.

Symptoms

  • Learning and development: Increased risk of learning disabilities and delayed development of speech and language skills.
  • Motor skills: Potential delays in motor skills such as sitting and walking, and weak muscle tone (hypotonia).
  • Behavioral and emotional: Some individuals may experience behavioral or emotional difficulties.
  • Other health issues: Seizures or kidney abnormalities occur in approximately 10 percent of affected females.

Causes & Risk Factors

Females typically have two X chromosomes (46,XX). Trisomy X results from an error in cell division, leading to a total of 47 chromosomes (47,XXX). Some females have this extra chromosome in only some of their cells, a condition known as 46,XX/47,XXX mosaicism.

Inheritance

Trisomy X is generally not inherited. It usually occurs as a random event during the formation of reproductive cells (eggs or sperm) due to an error called nondisjunction. Mosaicism also occurs as a random event during early embryonic development.

Frequently Asked Questions

Yes. Baseline renal ultrasound is advised because of a 10 % risk of kidney anomalies. Periodic EEG or neurologic exam is reasonable if seizures are reported. Additionally, monitor growth, thyroid function, and psychosocial development annually, and provide routine audiology and ophthalmology exams.
Most women with trisomy X have normal fertility and can conceive without major obstetric complications. However, they have a slightly increased risk of premature ovarian insufficiency and may experience earlier menopause. Prenatal counseling is recommended, as there is a small (<1 %) chance of transmitting an extra X chromosome to offspring. Regular obstetric care with attention to hormonal status is advisable.
Post‑natal diagnosis is usually made with a karyotype or chromosomal microarray from a blood sample when developmental concerns arise. Prenatally, non‑invasive prenatal testing (NIPT) can flag an extra X chromosome, but definitive confirmation requires chorionic villus sampling or amniocentesis with karyotyping.
Early intervention is key: speech‑language therapy focusing on articulation and expressive language, plus individualized education plans (IEPs) that incorporate visual supports, small‑group instruction, and occupational therapy for fine‑motor challenges. Structured routines, frequent breaks, and assistive technology (e.g., audiobooks, speech‑to‑text apps) can further enhance academic performance.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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