Paeds SAQs · genetics-dysmorphology-and-metabolism
Mitochondrial disease
Short-answer question on the tiered diagnostic approach to a child with suspected mitochondrial disease, including the dual-genome logic, the significance of lactate sensitivity, and the critical pharmacological contraindications.
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Prompt
A 2-year-old boy presents with refractory seizures, developmental regression, and hepatomegaly following a febrile illness. Blood gas shows a metabolic acidosis with lactate 6.8 mmol/L. Brain MRI reveals bilateral symmetric T2 hyperintensity in the basal ganglia and brain stem. His older sibling died in infancy of liver failure of unknown cause.
**(a)** What is the most likely diagnostic category, and what two genetic mechanisms must you consider when counselling the family? *(4 marks)*
**(b)** Outline your tiered investigation plan, including the rationale for testing both genomes. *(8 marks)*
**(c)** What is the single most important pharmacological contraindication in this child until a specific genetic diagnosis is secured, and why? Name a safer alternative. *(4 marks)*
**(d)** List four precipitants of metabolic decompensation in mitochondrial disease and state the principle of their management. *(4 marks)*
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