Bismuth Toxicity Masquerading as Alzheimer's Dimentia

By William K. Summers, MD
CASE REPORT
Journal of Alzheimer's disease - 1998

ABSTRACT: A 76-year old white married female had rapid onset dementia with myoclonus and was admitted to an HMO hospital where she was initially diagnosed with Alzheimer's disease. The physician-husband suggested that the condition might be due to the Pepto-Bismol which she had taken chronically to control her irritable bowel syndrome. An elevated serum bismuth level of 242 ug/L (normal is 5 ug/L) established bismuth toxicity as the cause of the dementia. With treatment, the patient returned to a normal mental state. The possibility of bismuth encephalopathy needs to be considered in the differential diagnosis of possible Alzheimer's dementia.

INTRODUCTION: Bismuth was used in medicinal salves as early as 1733, and internally for treatment of spasmodic bowels by the 1790s. Bismuth preparations are generally considered very safe and are often taken without knowledge of possible, albeit rare, neurotoxicity. Bierer's review of bismuth subsalicylate (Pepto-Bismol) states that there have been no cases of neurotoxicity in the United States (1). However, Gordon et al. reported a case of a 54-year old man with suspected bismuth encephalopathy, who had taken between 4 - 16 oz of Pepto-Bismol per day (1.04-4.16 mg/day of bismuth) intermittently over many years to control gastrointestinal upset and diarrhea (2). Unfortunately, the diagnosis was not suspected until the 35th day after the onset of his confusion, and the serum bismuth level was only 3.6 ug/L in the serum. Typically, bismuth encephalopathy does not occur without serum levels above 150 ug/L (7). We report below the case of bismuth encephalopathy with a serum bismuth level of 242 ug/L, which was initially incorrectly diagnosed as Alzheimer's disease.

CASE REPORT On February 29, 1996, a 76-year old Caucasian female was admitted to a local HMO hospital with a one-week history of progressive confusion, poor appetite, disturbed sleep and muscle twitching. Her physician-husband noted that she became lost in their retirement complex when attempting to do the laundry and that she complained of feeling like "coming out of a binge". She would take up to an hour to figure out how to put on her pajamas. Pertinent negatives included no history of fever, stiff neck, headache, emesis, and diarrhea or alcohol abuse. The past medical history was of migraine headaches, gastritis secondary to aspirin, Sjogren's disease, multiple food allergies with malabsorption of wheat, corn, milk and citrus products, and hypothyroidism. Trials on pancreases in the past did not help the malabsorption. Her medications on admission were Inderal 10 mg bid for migraine, Armor thyroid 2 gr. QAM, Premarin 0.625 mg qAM, Geritol multiple vitamin qAM, stress tablet biw, benign class; that is, inorganic salts which are insoluble in water (3).

An "epidemic outbreak" of over 1,000 cases of bismuth encephalopathy was reported between 1973-1980 in France and Australia (2). Seventy-two of these intoxications were fatal. Most occurred with chronic high-dose use of bismuth subnitrate or bismuth subgallate (3). Since 1980, case reports of bismuth encephalopathy have been infrequent. Nevertheless, there is higher risk of such cases because of the ready availability of bismuth salts and the increased use of Bismuth preparations in the treatment of Heliobacter pylori related gastric and duodenal ulcers (4).

In consideration of this specific patient, the diagnosis should have been suspected from the outset. Alzheimer's disease is an unrelenting progressive neurodegenerative disorder of insidious onset that leads to death, on average, 8 years after onset. Myoclonus is a very late and infrequent feature of Alzheimer's disease. Bismuth toxicity typically presents subacutely with mental changes of memory loss, psychosis and depression, with a prominent background of ataxia, tremors, myoclonus and seizures (4). In the present case, the onset was about a week, myoclonus was a prominent feature, and although unstated in the initial HMO evaluation, it was obvious that the patient had ataxia. The present case is a testimony for the need of differential diagnosis evaluation of the demented patient. All too often, the diagnosis of Alzheimer's disease is casually assigned. This practice must be discouraged. This case also points out the role of active treatment of the dementia aspects of patients. She was able to return to a normal life, possibly months before anticipated, because of the use of Tacrine. Finally, this case exemplifies the reason that it is logical to test bismuth in the "heavy metal screen."

References:

The NM Senior Citizen News publishes these articles monthly. You can pick up a copy of the paper at your closest New Mexico Senior Citizen Center.