Tardily accelerated neurologic deterioration in two-step thallium intoxication

Area of Science:

• Toxicology
• Neurology
• Environmental Health

Background:

• Thallium intoxication is known from single exposures, but the clinical course of repeated or divisional ingestion remains poorly understood.
• Previous reports primarily documented acute, one-time thallium poisonings.
• Understanding diverse exposure scenarios is crucial for accurate diagnosis and management of thallium toxicity.

Observation:

• A 16-year-old presented with two distinct episodes of thallium sulfate ingestion over 52 days.
• Initial symptoms after the first ingestion included gastrointestinal distress, alopecia, followed by delayed neurological deficits (vision loss, myalgia, leg weakness).
• The second ingestion led to rapid, severe neurological deterioration without concurrent gastrointestinal or cutaneous symptoms, indicating cumulative effects.

Findings:

• Brain MRI revealed bilateral optic nerve atrophy, and nerve conduction studies showed severe peripheral neuropathy.
• Urine analysis confirmed elevated thallium levels, diagnosing thallium intoxication.
• Neurological symptoms largely improved over two years, though visual loss was persistent, suggesting long-term neurotoxic impact.

Implications:

• This case demonstrates that divisional thallium intoxication can cause delayed, accelerated neurological deterioration, primarily affecting the optic and peripheral nervous systems.
• The findings suggest thallium's cumulative neurotoxicity, with a longer elimination half-life in nervous tissue contributing to progressive damage.
• Clinicians should consider repeated or low-dose thallium exposure in cases of unexplained progressive neuropathy, even without typical acute symptoms.