Nephrotic syndrome associated with thallium poisoning: a case report

Thallium is an extremely toxic metal with historical uses in medicine, pesticides, and industry. Thallium poisoning is rare but can occur through accidental or occupational exposure, leading to severe systemic effects, including polyneuropathy, gastrointestinal symptoms, and alopecia. Although heavy metal exposure is known to cause renal injury, nephrotic syndrome as a manifestation of thallium toxicity is poorly documented. We present the case of a previously healthy 27-year-old Mexican mestizo man who developed progressive lower limb edema, anasarca, hair loss, weight loss, and neurological deterioration after working as a sugarcane harvester. Initial evaluations suggested nephrotic syndrome with proteinuria of 6.9 g/24 hours, hypoalbuminemia, and hyperlipidemia. His condition worsened despite treatment with prednisone, methotrexate, and immunoglobulin, leading to referral to our hospital. Examination revealed quadriparesis, alopecia, and Mees' lines, prompting suspicion of heavy metal poisoning. Elevated thallium levels in serum and urine confirmed the diagnosis. A renal biopsy showed findings consistent with minimal change disease. d-Penicillamine treatment started but was stopped due to worsening proteinuria. Corticosteroids were subsequently administered, though follow-up was lost due to loss of social security benefits. This case highlights the nephrotoxic effects of thallium, presenting as nephrotic syndrome with minimal change disease, a finding not previously reported in the literature. The classic triad of thallium poisoning—polyneuropathy, gastroenteritis, and alopecia—remains an essential diagnostic clue, but renal involvement should also be considered. Prompt recognition and management of thallium poisoning are crucial to preventing severe complications. Further studies are needed to better understand thallium-induced nephropathy.