Tetrasomia

Tetrasomy is a rare chromosomal abnormality characterized by the presence of four copies of a particular chromosome instead of the usual two. This condition can occur in autosomes or sex chromosomes. When it affects autosomes, it is usually lethal and results in miscarriage. If a fetus with autosomal tetrasomy survives to term, it is typically associated with severe developmental abnormalities.

The most common form of tetrasomy seen in live births involves the sex chromosomes. Tetrasomy X, also known as XXXX syndrome, affects females. Individuals with this condition typically have a female phenotype but may experience a range of physical and intellectual characteristics. These can include developmental delays, learning disabilities, and certain physical features such as a small head, upslanting palpebral fissures, and a short neck. Ovarian development may be affected, leading to infertility or reproductive challenges.

Tetrasomy is a condition that arises from a meiotic error, specifically nondisjunction, during gamete formation in one of the parents. This leads to a sperm or egg cell with an extra chromosome. When this gamete fuses with a normal gamete during fertilization, the resulting zygote will have four copies of that specific chromosome. Diagnosis is typically made through genetic testing, such as karyotyping or chromosomal microarray analysis, which can identify the extra chromosome. Management of tetrasomy focuses on addressing the specific symptoms and developmental needs of the affected individual through supportive therapies and medical interventions.