We report a pediatric patient with an undiagnosed and complex medical manifestation who was shown to have paternal isodisomy at chromosome 7. Our case is a female patient presented for increasing overweight, parotid hemangioma and gastroesophageal reflux with laryngomalacia. She was born at 35+4 weeks of gestation and her birth weight, length and occipitofrontal circumference (OFC) were 2500 g, 49 cm and 33 cm, respectively. At the time of our visit she was 16 months old, her weight was 16.9 kg and her BMI 23.95. In order to detect the molecular basis of this extreme weight gain, we decided to perform whole-exome sequencing (WES) on genomic DNA isolated from peripheral blood leucocytes of the proband and her parents: WES data analysis resulted normal, with no detection of any sequence variants clearly associated with overgrowth phenotypes.. The analysis using SNP-CGH probes suggested that the genome of the patient had a loss of heterozygosity without any CNVs in chromosome 7, which implied that she had paternal isodisomy of the entire of chromosome 7 (IsoD7pat). IsoD7pat is extremely rare, and only four cases have been previously reported. As these cases were accompanied by autosomal-recessive disorders which are likely to be involved in growth restriction, the relevance of isoD7pat to the overgrowth phenotype remains unclear. Maternal uniparental disomy for chromosome 7 is known to result in Silver-Russel syndrome, characterized by intrauterine growth retardation accompanied by postnatal growth deficiency, but little is known about isoD7pat, which is extremely rare. Up to now, the other four reported patients did not express overweight, probably due to their autosomal recessive underlying condition (cystic fibrosis, primary ciliary dyskinesia, congenital chloride diarrhoea), to be involved in their growth restriction. We here report the second case of the isoD7pat, without autosomal-recessive disorders, expressing a clear overweight, supporting the involvement of this imprinting disorder in determinism of overgrowth phenotypes.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology