Ring Chromosomes Aberrations at a Pediatric Mexican Hospital. Two Cases with Mosaisism of Chromosome 13, 46XY / 46, XY, R (13) and Chromosome 18, 46, XY / 46, XY, R (18)

The autosomic alteration due to a ring formation is a rare aberration of either chromosome 13 and 18 which is in relation with phenotipic malformations, neurologic problems and genital abnormalities. Two clinical polymalformed cases with skull treboliform dismorfies with early seizures and malformed genitals with micropenis is presented from four of the total patients found in this study. Among chromosomic alterations, the ring of autosomic chromosome 13 and 18 are not frequent, the main phenotipical alterations in this study are in relation to neurological, genital and craniofacial malformations. Taking in consideration that mutations or chromosome aberrations are alterations in the chromosome number or structure. They are mainly considered due to gametogenesis inborn error (meiosis) or during the zygote first cellular divisions. All these alterations might be observed during metaphase from the cellular cycle, where DNA loses are seen due to DNA repair processes deficiency o total absence, among others. 4617 chromosomal studies were performed at Hospital Para El Nino Poblano (Pediatric Hospital) in Mexico (from 1992 to 2011) were 34.6% (1596 patients) showed different chromosomal alterations and only two patients showed ring chromosome aberrations. These chromosome changes are classified as structural alterations. Both pediatric patients with these genetic diseases are described in this study analyzing their clinical characteristics, medical or surgical treatments according to the phenotypic alterations.