Related Experiment Video

Updated: Aug 11, 2026

Visualization of Mitochondrial Respiratory Function using Cytochrome C Oxidase / Succinate Dehydrogenase (COX/SDH) Double-labeling Histochemistry
06:53

Visualization of Mitochondrial Respiratory Function using Cytochrome C Oxidase / Succinate Dehydrogenase (COX/SDH) Double-labeling Histochemistry

Published on: November 23, 2011

Mitochondrial electron transport chain defect presenting as hypoglycemia

M L Freckmann1, D R Thorburn, D M Kirby

  • 1Department of Clinical Genetics, Western Sydney Genetics Program, Australia.

The Journal of Pediatrics
|March 1, 1997
PubMed

Insights

A profoundly deaf infant with hypoglycemia and lactic acidosis had combined defects in electron transport chain (ETC) complexes I, III, and IV. This highlights the clinical diversity of ETC defects and their potential mimicry of fatty acid oxidation disorders.

Area of Science:

  • Biochemistry
  • Genetics
  • Pediatrics

Background:

  • Electron transport chain (ETC) disorders are a group of heterogeneous genetic conditions affecting cellular energy production.
  • Hypoglycemia and lactic acidosis in infants can be caused by various metabolic derangements, including glycogen storage diseases and fatty acid oxidation disorders.

Observation:

  • A profoundly deaf female infant presented with hypoglycemia and lactic acidemia following decreased oral intake and vomiting.
  • Enzyme studies of the ETC revealed combined defects in complexes I, III, and IV specifically in liver tissue, but not in skeletal muscle.

Findings:

  • The patient's presentation of hypoglycemia and lactic acidosis, coupled with specific ETC enzyme deficiencies, underscores the clinical heterogeneity of these disorders.
  • The biochemical profile observed in this case mimicked that of a fatty acid oxidation disorder, suggesting potential diagnostic overlap.

Implications:

  • Electron transport chain defects should be considered in the differential diagnosis of unexplained hypoglycemia and lactic acidosis in infants, even without a known glycogen storage disorder.
  • This case emphasizes the importance of comprehensive metabolic investigations, including ETC enzyme analysis, for accurate diagnosis and management of complex pediatric metabolic conditions.
  • Recognizing the potential for ETC defects to present with biochemical features resembling fatty acid oxidation disorders is crucial for timely and appropriate clinical intervention.

More Related Videos

Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle09:40

Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle

Published on: January 19, 2017

Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess07:35

Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess

Published on: June 1, 2022

Related Concept Videos

Electron Transport Chain: Complex I and II01:46

Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
Inborn Errors of Metabolism01:20

Inborn Errors of Metabolism

Phenylketonuria (PKU) is a protein metabolism disorder characterized by high blood levels of the amino acid phenylalanine. This results from a mutation in the gene responsible for phenylalanine hydroxylase, an enzyme that converts phenylalanine into tyrosine. When this enzyme is deficient, phenylalanine builds up in the blood, leading to symptoms such as vomiting, rashes, seizures, growth deficiency, and severe mental retardation. An early diagnosis and a diet restricting phenylalanine intake...
Hypoglycemia01:26

Hypoglycemia

Hypoglycemia is a blood glucose level below 70 mg/dL. It commonly occurs in individuals using insulin or insulin-secreting drugs, but may also arise in non-diabetic conditions. People with type 1 diabetes are at the highest risk because they depend on exogenous insulin. People with type 2 diabetes are also at risk, especially when treated with insulin or medications such as sulfonylureas, which increase insulin release regardless of blood glucose levels. It develops when insulin levels exceed...
Hyperglycemia01:29

Hyperglycemia

Hyperglycemia is an abnormally high blood glucose level. It is diagnosed by fasting glucose ≥126 mg/dL, 2-hour oral glucose tolerance test (or OGTT) ≥200 mg/dL, random glucose ≥200 mg/dL with symptoms, or HbA1c ≥6.5%. However, HbA1c results may be unreliable in certain conditions, such as anemia or hemoglobinopathies, and the diagnosis should be confirmed unless classic symptoms are present. Postprandial hyperglycemia is typically considered significant when glucose levels exceed 180 mg/dL two...
Diabetic Ketoacidosis ll: Pathophysiology01:22

Diabetic Ketoacidosis ll: Pathophysiology

Diabetic ketoacidosis (DKA) is a metabolic emergency characterized by hyperglycemia, ketonemia, and metabolic acidosis. It results from severe insulin deficiency and an excess of counterregulatory hormones, leading to uncontrolled lipolysis, ketogenesis, and widespread electrolyte and fluid disturbances.Pathophysiology The central event in DKA is a profound loss of insulin action. Without insulin, glucose uptake in insulin-dependent tissues is impaired, while hepatic glucose production...