Cat eye syndrome

Cat Eye Syndrome is a very rare malformation involving Chromosome 22. The short arm (p) and a small section of the long arm (q) are present three (trisomic) or four times (tetrasomic) instead of the usual two times. The additional chromosome 22 usually arises spontaneously (de novo), though it has been reported to have been passed down in families, and some reports show the parents as mosaic for the marker chromosome but who show no phenotypic (outer) symptoms of the syndrome.

The chromosomal area included in the Cat Eye Syndrome "critical region" is 22pter-->q11.

Partial trisomy of chromosome 22 resulting from an interstitial duplication of 22q11.2 in a child with typical cat eye syndrome

History

The first association of the common abnormalities common to CES was established over 100 years ago (1898) by Haab, and first described in association with a small marker chromosome in 1965 by Schachenmann.

A first report of a familial trisomy 22 pter-->q11happened in 1972 by Bühler et al. Early reports of Cat Eye Syndrome discuss the possibility of chromosome 13 involvement. Now, CES is considered to be present with the chromosome 22 trisomy findings.

Genetics

22q11.2 is a very unstable region of chromosome 22, which is involved in other syndromes, such as 22q11 deletion (a microdeletion of that area of the chromosome) and supernumerary der(22) syndrome, also known as trisomy 22 or partial trisomy 11/22.

Presentation

The most common association of symptoms include coloboma of the iris, renal abnormalities, and imperforate anus. Life expectancy is not significantly reduced in those patients who do not present with life threatening abnormalities.

The term "Cat Eye" syndrome was coined due to the particular appearance of the vertical colobomas in the eyes of some patients. However, over 1/2 of the CES patients in the literature do not display this trait.

Characteristics

• Anal atresia (abnormal obstruction of the anus)
• Unilateral or bilateral iris coloboma (absence of tissue from the colored part of the eyes)
• Palpebral fissures (downward slanting openings between the upper and lower eyelids)
• Preauricular pits/tags (small depressions/growths of skin on the outer ears)
• Cardiac defects
• Kidney problems (missing, extra, or underdeveloped kidneys)
• Short stature
• Scoliosis/Skeletal problems
• Mental retardation -- although most are borderline normal to mildly retarded, and a few even have normal intelligence, CES patients occasionally exhibit moderate to severe retardation.
• Micrognathia (smaller jaw)
• Hernias
• Cleft palate
• Rarer malformations can affect almost any organ