Four new cases are reported in which mosaicism for a supernumerary chromosome interpreted as an isochromosome for 12p [i(12p)] is present. In 2 cases seen in early childhood the mosaicism was present at a low level in peripheral blood and was documented in one case to be present with a higher frequency in fibroblast cultures from skin. These cases have clinical features compatible with those in previously reported cases of the Teschler-Nicola/Killian syndrome, many of whom have now been found to be mosaic for a similar i(12p) chromosome in fibroblast cultures. One case was diagnosed prenatally from amniotic fluid culture. The fourth case was a neonatal death, in which fibroblast cultures were established from muscle and increased activity of LDH-B was demonstrated, supporting the theory that the origin of the additional chromosome was from 12p. Loss of the cell line with the supernumerary chromosome occurs after long-term fibroblast culture. Previously unpublished studies showing increased LDH-B activity in case 1 of Pallister-Mosaic syndrome originally reported in 1977 are also reported. It is of interest that our 2 cases which did not survive birth and one previously published case diagnosed prenatally had diaphragmatic herniae.
We describe the first case of a baby with maternal uniparental disomy of chromosome 2. Growth failure, hypothyroidism, and hyaline membrane disease were present at birth, and the first year of life was complicated by bronchopulmonary dysplasia. At age 14 months, motor and intellectual development were normal, but growth remained below the 10th centile. The baby was investigated for uniparental disomy because trisomy 2 mosaicism had been detected in a second trimester amniocentesis. This is the first reported case in which amniotic fluid chromosome mosaicism has been associated with uniparental disomy. Implications for prenatal diagnosis are considered.
Clinical exome sequencing (CES) is increasingly being used as an effective diagnostic tool in the field of pediatric genetics. We sought to evaluate the parental experience, understanding and psychological impact of CES by conducting a survey study of English-speaking parents of children who had diagnostic CES. Parents of 192 unique patients participated. The parent's interpretation of the child's result agreed with the clinician's interpretation in 79% of cases, with more frequent discordance when the clinician's interpretation was uncertain. The majority (79%) reported no regret with the decision to have CES. Most (65%) reported complete satisfaction with the genetic counseling experience, and satisfaction was positively associated with years of genetic counselor (GC) experience. The psychological impact of CES was greatest for parents of children with positive results and for parents with anxiety or depression. The results of this study are important for helping clinicians to prepare families for the possible results and variable psychological impact of CES. The frequency of parental misinterpretation of test results indicates the need for additional clarity in the communication of results. Finally, while the majority of patients were satisfied with their genetic counseling, satisfaction was lower for new GCs, suggesting a need for targeted GC training for genomic testing.
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