Anorexia Nervosa and Mercury Toxicity

Mercury toxicity secondary to the excessive consumption of tuna was observed in a 47-year-old woman with a 30-year history of anorexia nervosa. The patient’s prolonged abuse of laxatives resulted in a small bowel obstruction and rectal prolapse 7 years prior to the detection of mercury intoxication. The rectal prolapse was treated with total proctocolectomy and ileostomy. A low fiber diet was recommended thereafter, and the patient commenced a diet consisting of two cans of tuna and one muffin daily for the subsequent 7 years until she came to our unit for observation and treatment of anorexia nervosa.

The patient presented with a 1-month history of depressive symptoms, refusal to eat, fatigue, weakness, anxiety, insomnia, irritability, and “confusion.” She weighed 73.7 lbs, which was approximately 53% of her ideal body weight, and was afraid that her bowels would stop working. She reported increased sensitivity to loud noise and ringing sounds in the absence of auditory stimuli. A neuropsychological assessment revealed less than normal scores for processing speed, working memory, and attention. Her premorbid IQ was estimated within the 61st percentile. Her current full-scale intelligence quotient score was within the 45th percentile, with a verbal intelligence quotient score within the 75th percentile and a performance IQ score within the 30th percentile. Her memory was stronger for verbal information (scoring in the 50th percentile) relative to nonverbal information (scoring in the 4th–10th percentile). Psychiatric examination revealed longstanding symptoms consistent with anorexia nervosa, but due to her most recent symptoms of irritability and weakness as well as her neuropsychological deficits, a mercury level evaluation was obtained.

The patient’s plasma mercury levels were markedly elevated at 74 mcg/dl (normal=<10 mcg/dl) on two repeated measurements. A complete blood count, electrolytes, amylase, and lipase were all unremarkable, but liver enzymes showed slight elevation. The patient underwent chelation therapy, with succimer 10 mg/kg t.i.d. for 5 days and then 10 mg/kg b.i.d. for the following 14 days. The mercury toxicity motivated her to change her diet and broaden her food repertoire. Although her attitudes toward food with high residue did not change, the patient became afraid of eating any type of fish.