A child presents with severe colicky abdominal pain, constipation, and a violaceous-grey gingival line (Burton's line). X-ray abdomen shows radio-opaque deposits in the large bowel. Blood smear shows basophilic stippling of RBCs. Which metal is responsible, and what is the pathomechanism of the gingival line?
- A Mercury — mercury sulphide deposits along gum margin
- B Bismuth — bismuth sulphide deposits along gingival margin
- C Lead — lead sulphide precipitating from circulating lead reacting with H₂S produced by sulphur-reducing oral bacteria ✓
- D Arsenic — arsenic trisulphide deposits in inflamed gum tissue
Explanation
Burton's line (lead line) is a classical sign of chronic lead poisoning. It forms when circulating lead (deposited in gingival tissues) reacts with hydrogen sulphide (H₂S) produced by sulphur-reducing anaerobic bacteria (particularly Treponema denticola) in the subgingival dental plaque, precipitating insoluble black lead sulphide (PbS) along the gum–tooth junction. The line appears grey-blue/violaceous and is typically 1 mm from the gingival margin. It is absent in edentulous individuals or those with excellent oral hygiene. Bismuth can produce a similar line (bismuth line) which is dark blue-black.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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Written and medically reviewed by the StethoPrep medical team.