A novel homoplasmic mt-tRNAGlu m.14701C>T variant presenting with a partially reversible infantile respiratory chain deficiency.

Abstract Background Reversible infantile respiratory chain deficiency (RIRCD) is a rare mitochondrial disorder associated with variable penetrance and partial to full remission of symptoms. Objective To describe features of maternally related individuals with a novel variant associated with RIRCD. Materials and methods Nine maternally related individuals aged 23 months to 64 years are described through physical examinations, muscle biopsies, histochemical and biochemical analyses, genome sequencing, and cerebral imaging. Results A homoplasmic mitochondrial transfer ribonucleic acid for glutamic acid (mt-tRNAGlu) m.14701C>T variant was identified in eight tested individuals out of nine maternally related individuals. Two individuals presented with hypotonia, muscle weakness, feeding difficulties and lactic acidosis at age 3–4 months, and improvement around age 15–23 months with mild residual symptoms at last examination. One individual with less severe symptoms had unknown age at onset and improved around age 4–5 years. Five individuals developed lipoma on the upper back, and one adult individual developed ataxia, while one was unaffected. Conclusions We have identified a novel homoplasmic mt-tRNAGlu m.14701C>T variant presenting with phenotypic and paraclinical features associated with RIRCD as well as ataxia and lipomas, which to our knowledge are new features associated to RIRCD.