Cat Eye Syndrome

What is Cat Eye Syndrome?

Cat Eye Syndrome, also known as Schmidt-Fraccaro syndrome is a rare genetic condition. It is a chromosomal disorder that is usually evident at birth. The name of the syndrome is due to the eye abnormality present in some affected individuals. The eye anomaly is due to absence of ocular tissue- coloboma that can affect one or both eyes ^[1].

What causes Cat Eye Syndrome?

Cat Eye Syndrome is caused by chromosomal abnormalities. In case of this disorder there is a presence of an extra part of chromosome 22. Normally human cells have two pairs of each chromosome. In case of this syndrome the short arm (p) and a small part of the long arm (q) of chromosome 22 is present three or even four times- trisomy or tetrasomy. In other cases only a part of the body cells have the extra chromosomal material- condition known as genetic mosaicism (also see mosaic Down syndrome). Other syndromes with an extra chromosome include: Edwards syndrome, Triple X syndrome.

The part of the long arm of chromosome 22- 22q11 is believed to be responsible for all or most of the clinical features. The exact cause of this syndrome is not yet understood. Usually there is no positive family history of this condition. Extra genetic material appears randomly. In case of mosaicism this abnormality can be transmitted through many generations, but the expression of symptoms is variable ^[2,3].

Symptoms

The symptoms of CES are very variable. They might range from mild, almost unnoticeable features to severe, life threatening problems. During the prenatal period, only small growth retardation is observed. Many of the symptoms are similar to one´s found in Goldenhar syndrome. Patients with mild CES usually have:

• Misshapen ears
• Downslanting eye-lid fissures
• Hyperteorism- wide set eyes
• Strabismus (crossed eyes)
• Flat nasal bridge
• Small jaw ^[4]

Eye anomalies

Depending on the severity of the condition, there can be various eye malformations. The most common eye defect is coloboma- a hole in a structure of eyes. It can be present in:

• Iris
• Choroid layer
• Optic nerve

Other eye anomalies include:

• Microphtalmia- small eye size, usually one-sided
• Aniridia- absence of iris
• Corneal clouding
• Cataract
• Strabismus ^[4]

Head and face malformations

One of the most common features found in patients with CES is cleft palate and/or cleft lip. Ear malformations can also occur- ears are misshapen and can have small holes or pits in front of them. Rare symptoms of the head and face region include:

• Choanal atresia
• Skin tags on the cheeks
• The outside part of ears can be reduced only to several skin tags. In this case atresia of external auditory canal is often present ^[4]

Gastrointestinal symptoms

Most common malformation of the gastrointestinal system is anal atresia- absent anal opening. In many cases this sign is combined with a fistula (abnormal opening) from the rectum in the bladder, vulva or vagina in females. In males rectum fistula can be present in the bladder, urethra or perineum. Other malformations of GI system are:

• Hernias of the abdominal wall
• Gut malrotation- an occurrence during fetal period, when the gut doesn’t completely rotate, creating various GI malformations.
• Meckel diverticulum- bulge in small intestine
• Hirschsprung disease-blockage of large intestine due to lack of muscle movements because of absence of nerves.
• Biliary atresia ^[4,5]

Skeletal symptoms

Skeletal malformations are not often present in CES, but they include:

• Radial aplasia- absence of a bone in the forearm
• Double or split big toe-hallux duplication
• Absent toes
• Sirenomelia
• Absence of rib joints
• Vertebral fusion (see Klippel-Feil syndrome)
• Spina bifida ^[4,5]

Other symptoms

• A common finding in persons with Cat Eye Syndrome is congenital heart defect, like TAPVR (Totally anomalous pulmonary venous return), Fallot tetralogy.
• Absence of one or both kidneys or malformation of kidneys is present in 50% of cases.
• Defects in lung segmentation
• Hypoplastic uterus
• Vaginal atresia (also see Androgen insensitivity syndrome)
• Hypospadias- the opening of the urethra on penis is unusually located
• Mild intellectual disability ^[4,5]

Diagnosis

The exact diagnosis of this syndrome can be made by using cytogenetic analysis. By using FISH assay (fluorescence in situ hybridization) the presence of extra chromosome 22 is found and it contains critical region of 22q11. Other diagnostic tests, such as imaging studies and laboratory analysis can be used to determine the extent of symptoms ^[5].

Differential diagnosis

• CHARGE syndrome
• VACTERL syndrome- vertebral anomalies, anal atresia, cardiac defect, trachea-esophageal fistula, renal abnormalities and limb anomalies^[5].

Treatment

Since Cat Eye Syndrome is a chromosomal disorder, the treatment is aimed to manage the symptoms.

If the patient has an abnormally short statue, it might be due to lack of growth hormone. In this case growth hormone therapy is used. Other medications depend on the severity of symptoms and the procedures used to treat them.

Surgical treatment might be necessary to manage anal atresia, cleft lip and severe congenital heart defects. In some cases eye malformations will require surgical intervention. Patients with this syndrome are susceptible to bacterial infections, therefore before and after any surgery anti-bacterial prophylaxis should be used.

In the presence of skeletal malformations and after surgery, physical therapy is often used. In case of intellectual disability other therapies can be used, like speech therapy and special education ^[6].

Prognosis

People with mild forms of CES don’t have a shorter life expectancy than an average person. However, those born with severe defect often die during infancy ^[5].

References

1. General patient information: http://www.webmd.com/parenting/baby/cat-eye-syndrome-facts#2
2. Causes and extended information about CES: https://rarediseases.org/rare-diseases/cat-eye-syndrome/
3. Genetics of CES: http://www.c22c.org/ces.htm
4. Symptoms: https://www.omim.org/entry/115470
5. Diagnosis and prognosis: https://rarediseases.info.nih.gov/diseases/26/cat-eye- syndrome
6. Treatment: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=195