Cat eye syndrome is a rare chromosomal disorder that may be evident at birth. Individuals with a normal chromosomal make-up have two 22nd chromosomes, both of which have a short arm, known as 22p, and a long arm, called 22q. However, in individuals with cat eye syndrome, the short arm and a small region of the long arm of chromosome 22 (i.e., 22pter-22q11) are present three or four times (trisomy or tetrasomy) rather than twice in cells of the body.
The name "cat eye syndrome" is derived from a distinctive eye (ocular) abnormality that is present in some affected individuals. This feature consists of partial absence of ocular tissue (coloboma), often affecting both eyes (bilateral). Affected ocular tissues may include the colored region (iris), the middle layer (choroid), and/or the nerve-rich innermost membrane (retina) of the eye.
Associated symptoms and findings may vary greatly in range and severity, including among affected members of the same family. While some may have few or mild manifestations that may remain unrecognized, others may have the full spectrum of malformations. However, in many cases, characteristic features of the disorder include mild growth delays before birth; mild mental deficiency; and malformations of the skull and facial (craniofacial) region, the heart, the kidneys, and/or the anal region.
More specifically, individuals with cat eye syndrome frequently have coloboma(s), downslanting eyelid folds (palpebral fissures), widely spaced eyes (ocular hypertelorism), and/or other ocular defects; misshapen ears with abnormal outgrowths of skin and small depressions in front of the outer ears (preauricular tags and pits), and/or absence (atresia) of the anal canal, with an abnormal passage (fistula) from the end portion of the large intestine (rectum) into abnormal locations (e.g., the bladder, vagina, or perineum). Additional features may commonly include variable congenital heart (cardiac) defects, kidney (renal) abnormalities, skeletal defects, and/or other physical findings.