Renal coloboma syndrome/dominant optic atrophy with severe retinal atrophy and de novo digenic mutations in PAX2 and OPA1

Renal coloboma syndrome (RCS) and dominant optic atrophy are mainly caused by heterozygous mutations in PAX2 and OPA1, respectively. We describe a patient with digenic mutations in PAX2 and OPA1. A female infant was born without perinatal abnormalities. Magnetic resonance imaging at 4 months of age showed bilateral microphthalmia and optic nerve hypoplasia. Appropriate body size was present at 2 years of age, and mental development was favorable. Color fundus photography revealed severe retinal atrophy in both eyes. Electroretinography showed slight responses in the right eye, but no responses in the left eye, suggesting a high risk of blindness. Urinalysis results were normal, creatinine-based estimated glomerular filtration rate was 63.5 mL/min/1.73 m2, and ultrasonography showed bilateral hypoplastic kidneys. Whole exome sequencing revealed de novo frameshift mutations in PAX2 and OPA1. Both variants were classified as pathogenic (PVS1, PS2, PM2) based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). Genetic testing for ocular diseases should be considered for patients with suspected RCS and a high risk of total blindness.