A 15-year-old boy is brought to the office by his parents due to worsening articulation and gait instability. His parents say that his speech has been increasingly difficult over the last 2 months, but he has had no difficulty with comprehension. The patient has also had progressive gait instability over the last month. He is falling more frequently and had to quit his basketball team. He has no chronic medical problems or allergies. The patient takes no medications and does not use alcohol or illicit drugs. Blood pressure is 120/70 mm Hg and pulse 80/min. Musculoskeletal examination shows scoliosis. Neurological examination reveals dysarthria and wide-based, unstable gait. There are absent deep tendon reflexes of the bilateral lower extremities. MRI of the brain and spinal cord shows marked atrophy of the medulla and dorsal columns of the spinal cord. This patient is at greatest risk of mortality from which of the following conditions?

A. Cardiac dysfunction

B. Diabetic nephropathy

C. Malignancy

D. Respiratory failure

E. Status epilepticus

Correct Answer: A. Cardiac dysfunction

🧠 Key Insight:

This 15-year-old boy presents with progressive dysarthria, gait instability, scoliosis, and absent deep tendon reflexes, along with MRI findings of atrophy of the medulla and dorsal columns. These findings are suggestive of Friedreich ataxia (FA), a autosomal recessive neurodegenerative disorder caused by mutations in the frataxin gene

🧠 Genetic Mutation

Frataxin gene mutation → ↓ frataxin protein
⬇
🧠 Mitochondrial Dysfunction

↓ mitochondrial iron regulation → mitochondrial damage
⬇
🧠 Oxidative Stress

↑ free radicals → neuronal damage
⬇
🧠 Dorsal Columns & Medulla Degeneration

Loss of proprioception and sensory input → sensory ataxia
⬇
🧠 Cerebellar Ataxia

Degeneration of cerebellum → gait instability, dysarthria
⬇
🧠 Scoliosis

Motor coordination loss → muscle weakness → scoliosis
⬇
🧠 Absence of Reflexes

Dorsal column involvement → absent deep tendon reflexes
⬇
🧠 Cardiac Involvement (Hypertrophic Cardiomyopathy)

Frataxin deficiency → impaired mitochondrial function in heart → hypertrophic cardiomyopathy
⬇
🧠 Cardiac Dysfunction

↑ risk of heart failure, arrhythmias → increased mortality
⬇
Correct Answer: A. Cardiac Dysfunction

Explanation of Other Options:

B. Diabetic Nephropathy

Diabetic nephropathy is caused by chronic hyperglycemia and vascular damage in the kidneys, not related to FA's mitochondrial dysfunction or neurodegeneration.

C. Malignancy

Malignancy is not a typical consequence of FA. While FA involves genetic mutations, cancer is not directly linked to the pathophysiology of the disease.

D. Respiratory Failure

While FA can lead to respiratory issues later due to weakened muscles, cardiac dysfunction is the leading cause of death, not respiratory failure.

E. Status Epilepticus

FA does not commonly present with seizures or epileptic episodes. The disease primarily affects the nervous system, leading to motor and sensory issues, not seizure activity.

Flashcards

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