Follow-up of two adult brothers with homozygous CEP57 pathogenic variants expands the phenotype of Mosaic Variegated Aneuploidy Syndrome

Mosaic Variegated Aneuploidy Syndrome (MVA) is a rare autosomal recessive disorder characterized by mosaic aneuploidies involving multiple chromosomes and tissues. Affected individuals typically present with severe intrauterine and postnatal growth retardation, microcephaly, facial dysmorphism, developmental delay and predisposition to cancer and epilepsy. Three genes, BUB1B, CEP57 and TRIP13, are involved in this syndrome. Only 7 patients carrying pathogenic variants in CEP57 are reported to date. Here we report two adult brothers born to Moroccan related parents, who presented with intrauterine and postnatal growth retardation, microcephaly, facial dysmorphism, learning disabilities, skeletal anomalies with thumb hypoplasia and dental abnormalities. Both brothers have mosaic variegated aneuploidies on blood karyotype. A previously reported homozygous 11 bp duplication was identified in CEP57 in the two brothers. We propose that a FoSTeS (Fork Stalling and Template Switching) mechanism could be involved in the occurrence of this duplication. This report expands the phenotypical spectrum associated with CEP57 and highlights the interest of blood karyotype in patients presenting with short stature and microcephaly.