Hyperkeratosis is a symptom most commonly associated with poisoning by which element?

• A. Arsenic
• B. Lead
• C. Mercury
• D. Cyanide

Answer: (A)

Chronic exposure to arsenic commonly produces distinct skin changes, with hyperkeratosis meaning thickening of the outer skin layer. This thickening, especially on the palms and soles, reflects arsenic’s effect on keratinocytes—disrupting their differentiation and promoting abnormal keratinization. Over time, these changes become a hallmark of arsenic poisoning, often seen alongside skin pigmentation changes and other signs like Mees’ lines in the nails.

The other substances listed don't produce this pronounced chronic skin thickening as a typical feature. Lead poisoning more characteristically affects the nervous system and blood (anemia), mercury can cause neurotoxic effects and tremors, and cyanide causes acute hypoxia and metabolic disturbances. Therefore hyperkeratosis points most strongly to arsenic poisoning.