Thallium Toxicity Clinical Presentation

Updated: Dec 12, 2021
  • Author: David Vearrier, MD, MPH; Chief Editor: Sage W Wiener, MD  more...
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The clinical presentation of thallium toxicity can vary depending on the type, severity, and timeframe of the exposure. Acute thallium poisoning is primarily characterized by gastrointestinal, neurological, and dermatological symptoms, while neurologic findings predominate with chronic exposure and tend to progress, even despite decreasing blood thallium levels. [6]

Gastrointestinal symptoms

These symptoms predominate early, usually within the first 3-4 hours, with the most common symptoms being abdominal pain with nausea/vomiting and diarrhea or constipation. [19, 20, 21] Unlike most other metal salt exposures, gastrointestinal findings in thallium toxicity may be mild or nonexistent, especially in chronic poisoning. Rarely, the vomitus and stools are bloody.

Neurologic symptoms

These symptoms usually appear 2-5 days (though some reports are for < 24 h) postexposure and include severely painful, rapidly progressive, ascending peripheral neuropathies. [19, 20] This is generally the reason patients seek medical care. Pain and paresthesias of the hands and the lower extremities, especially the soles of the feet, are also common. Distal motor weakness may follow, with the lower limbs more affected than the upper limbs. Ataxia, tremor, athetosis, cranial nerve palsies, headache, seizures, insomnia, coma, and death may also occur.

Neuropsychological manifestations may include anxiety, confusion, delirium, hallucinations, and psychosis. Acute agitation and aggression, personality changes, depression, apathy, and confabulation have been observed in both adults and children. Psychosis and associated symptoms can occur with or without a psychiatric history. [22]

Ocular symptoms

Diplopia, abnormal color vision, and impairment of visual acuity may develop. [23] Other manifestations may include alopecia of the lateral half of the eyebrows, skin lesions on the eyelids, ptosis, seventh nerve palsy, internal and external ophthalmoplegia, and nystagmus. Noninflammatory keratitis, lens opacities, and optic atrophy due to toxic optic neuropathy also may occur.

Dermatologic symptoms

The first cutaneous signs are not specific and include scaling of the palms and soles and acneiform or pustular eruptions of the face. [24] During weeks 2-3, a sudden onset of hair loss quickly progresses to diffuse alopecia. The hair loss primarily affects the scalp, temporal parts of the eyebrows, the eyelashes, and the limbs. Less often, the axillary regions are affected. Hair discoloration may also occur. One month after the poisoning, Mees lines (transverse white lines on the nails) appear in the nail plate. [25] Other dermatologic findings include crusted eczematous lesions, hypohidrosis, anhidrosis, palmar erythema, stomatitis, and painful distal glossitis. [26]

Other symptoms

Cardiovascular symptoms include tachycardia and hypertension. Significant ongoing tachycardia may be associated with a poor prognosis. [9]

Some patients can experience pleuritic chest pain or tightness upon exposure. The mechanism for this particular symptom is unclear.




Physical Examination

Focus the physical examination primarily on the organ systems most commonly affected.

Perform careful abdominal and rectal examinations, including stool guaiac tests. Abdominal tenderness, hyperactive bowel sounds, mild guarding, and guaiac-positive stools can be found as early findings in thallium intoxication.

Perform a detailed neurologic examination, including a complete cranial nerve and visual field assessment. Findings are as follows:

  • All cranial nerves (CN) can be affected by thallium. Nystagmus (fourth and sixth CN involvement) and ptosis (third CN) may be present.

  • Decreased lower extremity strength with the lower limbs more affected than the upper limbs, hyperesthesia (especially of the soles of the feet), and decreased sensation to pinprick, touch, temperature, vibration, and proprioception in the fingers and toes may be present.

Perform a slit lamp examination and funduscopic examination, and carefully document visual acuity and color perception. Findings are as follows:

  • Decreased visual acuity with impairment of contrast sensitivity and tritanomaly (blue color vision defect) may be observed. [23]

  • In the early stages of thallium toxicity, funduscopic examination may reveal signs of an optic neuritis characterized by a red and poorly defined papilla. Continued thallium exposure causes atrophy of the optic nerve, which results in the development of a pale or white papilla.

  • Noninflammatory keratitis and lens opacities are also described.

Perform a skin and scalp examination. Findings are as follows:

  • Early skin findings include scaling of the palms and soles and acneiform lesions of the face. [24]  Scalp alopecia, which is one of the most characteristic manifestations of thallium toxicity and is related to atrophy of the hair follicles, usually occurs 10-21 days postexposure. [27]  In addition to the scalp, hair loss also occurs in the lateral eyebrows, the eyelashes, the limbs, and occasionally the axillary regions.

  • Hair roots may have dark brown or black pigmentation as a result of the accumulation of gaseous inclusions that diffract the light. With chronic exposure, these darker regions appear in bands, demonstrating multiple thallium exposures.

  • Approximately 1 month after thallium exposure, Mees lines (transverse white lines on the nails) appear in the nail plate. [25]

  • Other dermatologic findings include well-demarcated hyperkeratosis of the palms and soles, crusted eczematous lesions, hypohidrosis, anhidrosis, palmar erythema, crusted perioral dermatitis, painful distal glossitis, and stomatitis. [26]