Maternal uniparental disomy of chromosome 20: a novel imprinting disorder of growth failure

Purpose: Maternal uniparental disomy of chromosome 20 (UPD(20) mat) has been reported in only four patients, three of whom also had mosaicism for complete or partial trisomy of chromosome 20. We sought to evaluate the clinical significance of isolated UPD(20) mat in eight individuals. Methods: We evaluated phenotypic and genomic findings of a series of eight new patients with UPD(20) mat. Results: All eight individuals with UPD(20) mat had intrauterine growth restriction, short stature, and prominent feeding difficulties with failure to thrive. As a common feature, they often required gastric tube feeds. Genomic data in most patients are indicative of UPD as a result of trisomy rescue after meiosis II nondisjunction. Conclusion: We describe the first natural history of the disorder and the results of therapeutic interventions, including the frequent requirement of direct gastric feedings only during the first few years of life, and propose that growth hormone supplementation is probably safe and effective for this condition. We suggest that UPD(20) mat can be regarded as a new imprinting disorder and its identification requires specialized molecular testing, which should be performed in patients with early-onset idiopathic isolated growth failure.