What are the risks and management strategies for an 18-year-old with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) who has developed a cold?

Yes, You Should Be Concerned—Infections Can Trigger Life-Threatening Metabolic Crises in MELAS

Your son's cold represents a significant risk because infections are known triggers for stroke-like episodes and metabolic decompensation in MELAS patients, and you need to act proactively now to prevent serious complications. 1, 2

Immediate Actions Required

Monitor for Warning Signs of Metabolic Crisis

Watch closely for these red flags that indicate he's progressing beyond a simple cold:

• Severe headache (migraine-like, which often precedes stroke-like episodes) 2, 3
• Seizures or altered consciousness (drowsiness, confusion) 1, 2
• Visual disturbances (cortical blindness can occur) 1, 4
• Nausea and vomiting (especially if persistent >24 hours) 5, 1
• Extreme fatigue beyond typical cold symptoms (exercise intolerance worsens) 2
• Breathing difficulties (respiratory distress, elevated respiratory rate) 5

Ensure L-Arginine Access

• Your son should have immediate access to L-arginine therapy, as this is the primary treatment for preventing and managing stroke-like episodes in MELAS 1, 6
• If he's not already on maintenance oral L-arginine (600 mg/kg/day for <20 kg or 12 g/m² for >20 kg), contact his physician about starting it during this illness 6
• If any warning signs develop, he needs intravenous L-arginine immediately at the same weight-based dosing given over 90 minutes, which can improve headache, nausea, impaired consciousness, and visual disturbances 1, 6

Why This Matters: The Pathophysiology

Infections as Metabolic Stressors

MELAS patients have impaired mitochondrial energy production due to the A3243G mutation (present in ~80% of cases), which disrupts cellular metabolism 1, 2. When infection increases metabolic demands:

• Energy-deficient cells cannot meet increased demands, particularly in high-energy organs like the brain 1
• Lactic acidosis worsens as anaerobic metabolism increases 1, 3
• Seizures can be triggered, which further elevate CO2 and worsen metabolic acidosis 1
• Stroke-like episodes can occur, with lesions that don't follow vascular territories but preferentially affect posterior brain regions 2, 7

The Rapid Progression Risk

Japanese cohort data shows MELAS patients demonstrate rapidly increasing disability scores (mean 12.8±8.7) within just 5 years from disease onset, and the juvenile form (onset <18 years) carries a 3.29-fold higher mortality risk than adult-onset disease 4. This means your son is in the higher-risk category.

Clinical Management Algorithm

Step 1: Supportive Care at Home (If Mild Cold Only)

• Aggressive hydration with fluids 5
• Antipyretics for fever (avoid aspirin in anyone under 16) 5
• Rest and avoid physical exertion (exercise intolerance is a cardinal feature) 2

Step 2: Contact Physician If Any of These Develop

• Fever >38.5°C 5
• Severe earache 5
• Vomiting >24 hours 5
• Any neurological symptoms (headache, visual changes, confusion) 1

Step 3: Emergency Department Immediately If:

• Signs of stroke-like episode: sudden neurological deficits, severe headache, visual disturbances, seizures 1, 7
• Altered consciousness or drowsiness 5, 1
• Respiratory distress: markedly raised respiratory rate, grunting, intercostal recession, breathlessness 5
• Signs of sepsis: extreme pallor, hypotension 5

Critical Pitfalls to Avoid

Don't Wait for "Typical" Stroke Symptoms

Stroke-like episodes in MELAS don't follow vascular territories and preferentially involve posterior brain regions, so symptoms may not look like typical strokes 2, 7. Any acute neurological change warrants immediate evaluation.

Don't Withhold Oxygen If Needed

If he develops hypoxemia, provide adequate oxygen—the mechanism of respiratory compromise in MELAS is fundamentally different from COPD, and oxygen should not be withheld 1.

Don't Assume It's "Just a Cold"

The relapsing-remitting nature of MELAS means that seemingly minor illnesses can trigger major metabolic crises 8. Seizures are a cardinal feature and can occur at any age in MELAS patients 1.

Monitoring During Illness

Check Serum Lactate If Symptoms Worsen

Elevated serum and CSF lactic acid levels are diagnostic hallmarks of MELAS, and rising lactate during illness indicates worsening metabolic stress 1, 3. If he requires hospital evaluation, lactate should be measured immediately 1.

Consider Prophylactic Antibiotics

While the evidence provided focuses on pandemic influenza management 5, children with chronic comorbid diseases (which includes MELAS) who develop high fever (>38.5°C) and respiratory symptoms should be assessed for bacterial superinfection and may benefit from antibiotics 5.

The bottom line: treat this cold as a potential trigger for serious complications, maintain a low threshold for seeking medical attention, and ensure L-arginine therapy is immediately available. 1, 6