NPHS2 and mitochondrial encephalomyopathy: In 7 of 8 (88%) primary nonresponders, genetic testing was performed and 2 patients were identified with a genetic cause: 1 patient was diagnosed with having mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes and another patient had 2 pathogenic variants in NPHS2 (compound heterozygous).