Which condition is characterized by paresthesias and tremor (mad hatter’s disease), emotional lability, polyneuropathies, and red fingers, toes, or cheeks?

• A. Mercury poisoning
• B. Arsenic poisoning
• C. Lead poisoning
• D. Cadmium poisoning

Answer: (A)

Mercury poisoning is being tested here. The tremor with paresthesias, often labeled as mad hatter’s disease, reflects the neurotoxicity and emotional changes (erethism) that come with mercury exposure. Chronic mercury exposure can also cause polyneuropathy and a red or pink appearance of the extremities and face, known as acrodynia or pink disease. This combination of tremor, mood/behavior changes, peripheral nerve involvement, and reddened digits is characteristic of mercury poisoning and helps distinguish it from other heavy-metal toxicities, which tend to show different signature symptoms (for example, arsenic with GI effects and skin changes, lead with abdominal/cognitive issues and wrist drop, cadmium with kidney and bone effects).