We report two cases of thallium intoxication by intravenous injection of contaminated heroin.

A 42-year-old male heroin user with the acquired immunodeficiency syndrome presented with a 15-day history of abdominal pain and alopecia. A search for thallium showed elevated blood (796 µg/L) and urine (5814 µg/L) thallium levels; within a few days, encephalopathy characterized by agitation and confusion ensued. On the eighth day, the patient's thallium levels were 443 µg/L in blood, 9180 µg/L in urine, and 20.4 µg/L in cerebral spinal fluid. His condition worsened with clouding of consciousness, fever, and respiratory distress. Bronchoalveolar lavage findings were consistent with those of aspiration. The patient died on the twelfth day.

Our second patient, a 48-year-old male heroin user, presented with an 8-day history of abdominal pain, cramps, and alopecia. Initial thallium levels were 3480 µg/L in urine. On day 21, thallium levels were 1795 µg/L in urine and 89.7 µg/L in blood. Electromyography detected an axonal sensory polyneuropathy in the lower extremities, and somatosensory evoked potentials showed delayed conduction in the peripheral nerves. The patient's course was marked by progressive clinical amelioration and reduced blood (51 µg/L) and urine (742 µg/L) thallium levels by day 28.

Thallium contamination was confirmed, but its cause remains unexplained. In thallium intoxication, the neurologic assault is associated with encephalopathy and peripheral neuropathy [1, 2], which is exclusively sensory (patient 2). The acute respiratory distress syndrome has been reported [3], and immunosuppression in combination with aspiration may have played a role in patient 1. The gravity of the clinical picture appears to be linked to the thallium levels in blood and urine and to the underlying health status of the patient. Other cases may appear, given that the source and magnitude of contamination remains unknown.