Diffuse mesangial sclerosis in a PDSS2 mutation-induced coenzyme Q10 deficiency

A 7-month-old male infant was admitted because he was suffering from nephrotic syndrome, along with encephalomyopathy, hypertrophic cardiomyopathy, clinically suspected deafness and retinitis pigmentosa, and an elevated serum lactate level. Coenzyme Q10 supplementation was started because of the clinical suspicion of primary CoQ10 deficiency. Despite intensive efforts, he passed away 4 weeks after admission. The results of genetic tests, available postmortem, explored two hitherto undescribed mutations in the PDSS2 gene. Both were located within the polyprenyl synthetase domain. Clinical exome sequencing revealed a heterozygous missense mutation in exon 3, and our in-house joint-analysis algorithm detected a heterozygous large 2923-bp deletion that affected the 5 prime end of exon 8. Other causative defects in the CoQ10 and infantile nephrosis-related genes examined were not found. A postmortem histological, immunohistochemical, and electron microscopic evaluation of the glomeruli revealed collapsing-sclerosing lesions consistent with diffuse mesangial sclerosis. The extrarenal alterations included hypertrophic cardiomyopathy and diffuse alveolar damage. A histological evaluation of the central nervous system and skeletal muscles did not demonstrate any obvious abnormality. Until now, the clinical features and the mutational status of 6 patients with a PDSS2 gene defect have been reported in the English literature. Here, we describe for the first time detailed kidney morphology features in a patient with nephrotic syndrome carrying mutations in the PDSS2 gene.