Cat-eye syndrome is a rare genetic syndrome of chromosomal origin. Individuals with
cat-eye syndrome are characterized by the presence of preauricular pits and/or tags,
anal atresia, and iris
coloboma. Many reported cases also presented with variable congenital anomalies and
intellectual disability. Most patients diagnosed with CES carry a small supernumerary bisatellited
marker chromosome, resulting in
partial tetrasomy of 22p-22q11.21. There are two types of small supernumerary
marker chromosome, depending on the breakpoint site. In a very small proportion of cases, other cytogenetic anomalies are reportedly associated with the
cat-eye syndrome phenotype. Here, we report a patient with
cat-eye syndrome caused by a type 1 small supernumerary
marker chromosome. The phenotype was atypical and included a severe developmental delay. The use of array comparative genomic hybridization ruled out the involvement of another chromosomal imbalance in the neurological phenotype. In the literature, only a few patients with
cat-eye syndrome present with a severe developmental delay, and all of the latter carried an atypical
partial trisomy 22 or an uncharacterized small supernumerary
marker chromosome. Hence, this is the first report of a severe neurological phenotype in
cat-eye syndrome with a typical type 1 small supernumerary
marker chromosome. Our observation clearly complicates prognostic assessment, particularly when
cat-eye syndrome is diagnosed prenatally.