Mosaicism for a small supernumerary chromosome 22 associated with dysmorphic features and early onset dementia

Abstract

A 46 -year old female was referred to the neurologist by her optometrist for a right homonymous superior field defect. As an infant, she was diagnosed as having multiple congenital abnormalities that included micrognathia which required several jaw surgeries, multiple ear tags as well as problems with rectal weakness which required surgery. She also indicated that for a couple of years she has been experiencing poor memory. On physical examination, she was noted to have a long narrow face with downward slanting palpebral fissures, a small jaw and mild scoliosis. Her mental status was within normal limits to language, comprehension and repetition.

Neuropsychology testing revealed impaired psychomotor ability, reduced executive functioning and border- line visual memory. A neuro-ophthalmologist confirmed the diagnosis of right homonymous superior quadranopsia probably due to a congenially smaller or dysplastic left occipital lobe. A SPECT scan showed decreased activity in the right temporal and bilateral superior parietal lobes consistent for the early stages of Alzheimer's disease.

Peripheral blood chromosome analysis revealed a mosaic karyotype, 47,XX+mar[3]/46,XX[17]. The marker chromosome was identified using whole chromosome paint probes and FISH analysis to be derived from chromosome 22. Some of the phenotypic features seen in this patient are similar to that of the Cat-eye syndrome which also has a supernumerary chromosome derived from chromosome 22. In addition, our patient seems to have symptoms of early onset dementia. It is not clear whether this is associated with the marker chromosome 22.