Mitochondrial Complex III Deficiency with Ketoacidosis and Hyperglycemia Mimicking Neonatal Diabetes
Hyperglycemia is a rare presenting symptom of mitochondrial disorders. We report a case of a young girl who presented shortly after birth with ketoacidosis, hyperlactatemia, hyperammonemia, and insulin-responsive hyperglycemia. Initial metabolic work-up suggested mitochondrial dysfunction. Given our patient’s unusual presentation, whole-exome sequencing (WES) was performed on the parent–offspring trio. The patient was homozygous for the c.643C>T (p.Leu215Phe) variant in CYC1, a nuclear gene which encodes cytochrome c 1 , a subunit of respiratory chain complex III. Variants in this gene have only been previously reported in two patients with similar presentation, one of whom carries the same variant as our patient who is also of Sri Lankan origin.
Primary complex III deficiencies are rare and its phenotypes can vary significantly, even among patients with the same genotype.
KeywordsComplex III CYC1 variant Neonatal diabetes Whole-exome sequencing (WES)
We gratefully acknowledge the family for their participation in this study; Mrs. X. Han for Sanger sequencing; Mr. B. Sayson and Ms A. Ghani for consenting and data management; and Mrs. M. Higginson for DNA extraction, sample handling, and technical data (University of British Columbia, Vancouver, CA).
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