Related Experiment Video
Updated: Nov 9, 2025
Author Spotlight: Unveiling Mitochondrial Function and Cellular Metabolic Adaptation in Metabolic Diseases
Published on: October 4, 2024
Muscle fat replacement and modified ragged red fibers in two patients with reversible infantile respiratory chain
Ana Cotta1, Elmano Carvalho2, AntonioLopes da-Cunha-Junior3
1Pathology Department, The SARAH Network of Rehabilitation Hospitals, Belo Horizonte, Brazil.
Abstract:
Reversible infantile respiratory chain deficiency is a severe neonatal mitochondrial myopathy that resolves spontaneously. It is caused by the homoplasmic m.14674T>C mtDNA mutation and additional nuclear variants in genes interacting with mt-tRNAGlu have been detected in some patients. We present detailed clinical, imaging, and muscle biopsy findings in a boy and a girl with neonatal hypotonia, feeding difficulties, lactic acidosis, and ragged red fibers. Both patients show fat replacement on muscle imaging, which was mild in the boy, but severe in the girl, affecting mostly the posterior leg muscles. In addition to the homoplasmic m.14674T>C, both patients carried heterozygous variants in QRSL1 (c. 686T>G; p.Val299Gly) and EARS2 (c.358C>T; p.Arg120Trp), respectively. It is very important to recognize the clinical and morphological signs of reversible infantile respiratory chain deficiency as patients should receive intensive supportive care in the first 6 months of life. Understanding the mechanism of the spontaneous recovery may lead to novel therapeutic perspectives in other mitochondrial diseases.
Insights
Reversible infantile respiratory chain deficiency, a neonatal mitochondrial myopathy, is linked to the m.14674T>C mtDNA mutation and nuclear variants. Early recognition and supportive care are crucial for recovery and potential therapeutic insights.
Area of Science:
- Mitochondrial Medicine
- Genetics
- Neonatal Neurology
Background:
- Reversible infantile respiratory chain deficiency is a severe neonatal mitochondrial myopathy.
- It is characterized by spontaneous resolution and is associated with the homoplasmic m.14674T>C mtDNA mutation.
Observation:
- Detailed clinical, imaging, and muscle biopsy findings were analyzed in two patients (a boy and a girl).
- Both presented with neonatal hypotonia, feeding difficulties, lactic acidosis, and ragged red fibers on muscle biopsy.
- Muscle imaging revealed fat replacement, mild in the boy and severe in the girl, predominantly in posterior leg muscles.
Findings:
- The m.14674T>C mtDNA mutation was identified as homoplasmic in both patients.
- Heterozygous variants in QRSL1 (c.686T>G; p.Val299Gly) and EARS2 (c.358C>T; p.Arg120Trp) were detected in the boy and girl, respectively.
- These nuclear variants interact with mt-tRNAGlu, suggesting a combined genetic contribution.
Implications:
- Recognizing clinical and morphological signs of this condition is vital for timely intervention.
- Intensive supportive care during the first six months of life is recommended.
- Understanding the spontaneous recovery mechanism may offer novel therapeutic strategies for mitochondrial diseases.
More Related Videos
09:40Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle
Published on: January 19, 2017
09:19A Guide to Examining Intramuscular Fat Formation and its Cellular Origin in Skeletal Muscle
Published on: May 26, 2022
Related Concept Videos
01:24Muscle Recovery and Fatigue
01:29Cardiomyopathy IV: Restrictive Cardiomyopathy