Everything about Xxxx Syndrome totally explained
XXXX syndrome (also called
tetrasomy X,
quadruple X, or
48, XXXX) is a rare
chromosomal disorder caused by the presence of four
X chromosomes instead of two X chromosomes, which are normally found in females. 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.
Causes and Diagnosis
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
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. 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.
Developmentally, tetrasomy X patients frequently show mild delays in the areas of speech development and articulation, language expression and understanding, and reading skills. Delays in motor development are also present, with walking ages ranging from 16 months to 4.5 years. About 50% of patients undergo
puberty normally, whereas the other 50% experiences no puberty, partial puberty without secondary sexual characteristics, or complete puberty with menstrual irregularities and/or early menopause (possibly as early as the teens). Medical literature reports four tetra-X pregnancies, two healthy, one with
trisomy 21, one stillborn with
omphalocele.
In terms of internal organ systems, tetrasomy X patients may have abnormal vision, hearing, circulatory systems, kidneys, or nervous systems. Disorders of the eye include
myopia,
nystagmus,
coloboma,
microphthalmus, or
optic nerve hypoplasia. In terms of hearing, patients are more prone to
ear infections, sound blockage, or nerve abnormalities. Several cardiac defects have also been reported, including
ventricular/atrial septal defects,
atresia,
hypoplastic right heart syndrome,
patent ductus arteriosus, and conotruncal or valvular cardiac defects. Tetrasomy X patients also appear to be more prone to seizure activity, although there's no documented abnormalities in brain function or structure when analyzed using an
ECG or
MRI.
Treatment and Prognosis
The general prognosis for girls with tetrasomy X is relatively good. Due to the variability of symptoms, some tetrasomy X girls are able to function normally, whereas others will need medical attention throughout their lives. Traditionally, treatment for tetrasomy X has been management of the symptoms and support for learning. Most girls are placed on estrogen treatment to induce breast development, arrest longitudinal growth, and stimulate bone formation to prevent osteoporosis. Speech, occupational, and physical therapy may also be needed depending on the severity of the symptoms.
Further Information
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