[Two patients with mitochondrial respiratory chain disease]

Area of Science:

• Biochemistry
• Genetics
• Neurology

Background:

• Mitochondrial respiratory chain diseases are complex genetic disorders affecting multiple organ systems.
• Diagnosis can be challenging due to the low sensitivity and specificity of standard laboratory tests.

Observation:

• Two patients, a woman and a boy, presented with symptoms of mitochondrial disease.
• The woman exhibited symptoms consistent with Kearns-Sayre syndrome, while the boy had nonspecific symptoms.
• Reduced activity of Complex 1 was identified as the underlying cause in both patients and the boy's mother.

Findings:

• Biochemical assessment of muscle biopsy is crucial for diagnosing mitochondrial diseases, revealing reduced ATP synthesis and specific complex abnormalities.
• DNA analysis can identify mitochondrial or nuclear mutations contributing to the disease.
• Reduced Complex 1 activity was the specific biochemical defect identified in this case.

Implications:

• Early and accurate diagnosis of mitochondrial diseases is essential for effective management.
• Targeted biochemical assessment, particularly of mitochondrial respiratory chain complexes, is vital when initial tests are inconclusive.
• While evidence is limited, cofactor replacement therapy (e.g., co-enzyme Q10, antioxidants) may help improve symptoms and stamina in patients with mitochondrial respiratory chain disease.