Non-Mosaic Tetrasomy 9p in An Infant With Multiple Congenital Anomalies

Abstract

Supernumerary isochromosomes resulting in autosomal tetrasomy are rare and have been described for 12p, 18p and 9p. To date, approximately 30 patients have been described with a tetrasomy 9p, majority of cases being mosaics. We present a new case of non-mosaic i(9p) that presented to us early in infancy with significant dysmorphological features including severe retardation, hypertelorism, cleft lip
and palate, micrognathia and low set malformed ears. Skeletal abnormalities were loss of some of the phalanxes, hypoplastic nails with mild syndactyly, limb contractures and dislocated hibs. The main difference between mosaic and non-mosaic infants is the poorer prognosis of non-mosaics. The infant died at 28th day of age, three days later of hospitalization.
Karyotype analysis of blood lymphocytes indicated an additional marker as an isochromosome in the size of E-16. The origin and structure of this additional marker could not be determined by chromosome banding. Application of fluorescence in situ hybridization identified the origin of marker chromosome as
isochromosome 9p, demonstrating the effectiveness of molecular cytogenetic investigation in the diagnosis of structural and numerical chromosomal abnormalities.