Short communicationPOLG mutation in a patient with cataracts, early-onset distal muscle weakness and atrophy, ovarian dysgenesis and 3-methylglutaconic aciduria

Mutations in POLG account for one of the most frequent nuclear encoded causes of mitochondrial disorders to date. Individuals harboring POLG mutations exhibit fairly heterogeneous clinical presentations leading to increasing difficulties in classifying these patients into defined clinical phenotypes. This study aims to investigate the molecular basis of a mitochondrial cytopathy in a patient with 3-methylglutaconic aciduria and to expand the clinical phenotype associated with POLG mutations.Clinical, molecular and genetic analyses as well as neurophysiological examinations were carried out for a 23-year-old woman of mixed Caucasian and Latin American ancestry with a history of cataracts diagnosed at age 1year, she had onset of distal muscle weakness at age 2years progressing to atrophy and ovarian dysgenesis at puberty. The patient was found to have 3-methylglutaconic acid with normal 3 hydroxyisovaleric acid on urine organic acid analysis. POLG sequencing was done and a heterozygous variant, c.2851T>A (p.Y951N) was found which is predicted to be deleterious. There are limited reports of POLG mutations in individuals with 3-methylglutaconic aciduria. This case report of a young woman with a heterozygous mutation in POLG, presenting with muscle weakness and atrophy at a young age aims to aid clinicians in similar challenging diagnostic situations as well as enhances our understanding of POLG-related disease phenotypes.

► We tested a 23-year-old female with suspected mitochondrial disease for POLG mutation. ► Patient was affected with distal muscle atrophy, cataract and ovarian dysgenesis. ► We also detected 3-methylglutaconic acid on urine organic acid analysis. ► We identified a heterozygous p.Y951N variant in POLG, predicted to be deleterious. ► These findings enhance our understanding of POLG-related disease phenotypes.