Case of supernumerary der22,T(11/22), born to a mother mosaic for the 11/22 translocation. M. Descartes, A. Carroll. Department of Pedicatris, Uviv. of AL. at Birmingham, AL.

   Our patient was the first child born to a 21 year old female at term by SVD. Her birth weight was 3.2kg (50th), her length was 53cm (50th), and her FOC measured 34cm (25th). She was noted at birth to have dysmorphic features and CHD(coartation of the aorta and AV canal). Her physical examination was pertinent for: malformed ears with preauricular pits and tags, fronto orbital hypoplasia, scarce eyebrows, flat nasal bridge, epicanthic folds, micrognathia, facial asymmetry, hypoplasia of the labia majora, anteriorly placed anus. Peripheral blood cytogenetic analysis revealed a 47,XX,+der(22)t(11;22)(q23;q11.2) karyotype. Maternal chromosome analysis of peripheral blood on 2 different occasions revealed that she was a mosaic carrier of the 11;22 translocation, mos46,XX,t(11;22)(q23;q11.2)/46,xx. Chromosome studies of the maternal grandparents revealed normal karyotypes for both. The t(11;22) is thought to be one of the most common reciprocal translocations in man. While most reported cases have been familial, at least 3 instances are known where the balanced t(11;22) occurred "de novo" in a carrier parent. Mosaicism for any balanced translocation is very rare and we are unaware of any previous report of mosaicism for the balanced t(11;22). We presume that our proband's mother's cells were initially normal, and that a very early somatic event led to the translocation that was present in approximately 50% of her PHA stimulated leukocytes. Chimerism seems unlikely, but has not been ruled out. The recurrence risk we quoted the mother was the same (2-6%) as that listed in the literature for non-mosaic carrier females.