RESUMO
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.