Implementation and experience of an alternative QF-PCR and MLPA diagnostic strategy to detect chromosomal abnormalities in fetal and neonatal pathology samples.

Chromosomal abnormalities are a significant cause of pregnancy loss. Solid tissue fetal and neonatal pathology samples are routinely examined by karyotype analysis after cell culture. However, there is a high failure rate, and this approach is expensive and labor intensive. We have therefore evaluated a new molecular strategy involving quantitative fluorescent polymerase chain reaction (QF-PCR) and subtelomere multiplex ligation-dependent probe amplification (MLPA) analysis. A retrospective audit showed that less than 4% of abnormal cases may not be detected by this molecular strategy. We validated this strategy in parallel with cytogenetic analysis on 110 patient samples, which included cases of fetal loss, still birth, neonatal death, termination of pregnancy, recurrent miscarriage, and sudden unexpected death in infancy. This validation showed that 55 of the 57 samples that gave a result for both strategies were concordant. During the 1st year of diagnostic testing, we analyzed 382 samples by the molecular strategy. A 16% abnormality rate was observed. These included trisomies 13, 18, 21, monosomy X, and triploidy detected by QF-PCR (77%), and 23% were other trisomies and subtelomere imbalances detected by MLPA. This strategy had a 92% success rate in contrast to the 20%-30% failure rate observed with cell culture and cytogenetic analysis. We conclude that QF-PCR and subtelomere MLPA is a suitable strategy for analysis of the majority of fetal and neonatal pathology samples, with many advantages over conventional cytogenetic analysis.

Mosaic trisomy 1q: The longest surviving case.

We present the longest known surviving case of a male infant with a mosaic complete trisomy 1q. Born at 39 weeks of gestation with respiratory distress, his weight was 3,330 g (25th centile); he had micrognathia, a posterior cleft of palate, abnormal ears and left thumb, syndactyly, and an absent corpus callosum. Initial blood karyotype was normal (46,XY). He died at age 5 months. Autopsy suggested aspiration as the primary cause of death and confirmed the antemortem findings of an absent corpus callosum and atrial septal defect. It also identified some central nervous system, cardiac, gastrointestinal, and lung anomalies not previously recognized. Cytogenetic analysis of skin fibroblasts obtained at autopsy showed a de novo unbalanced translocation between chromosomes 1 and 22: 46,XY,+1,der(1;22)(q10;q10)[25]/46,XY[65] in the cells examined. The previously reported cases had a similar phenotype with birth weight above the 50th centile for gestational age, small mouth, micrognathia, abnormal ears, abnormal fingers, microphthalmia, and hydrocephalus. The present case and a review of the literature delineates the phenotype in trisomy 1q, and reinforces the critical importance of effective communication between specialists, and obtaining permission for autopsy and skin biopsy, in the pursuit of a diagnosis.