A middle aged man presents with parasthesia of hands and feet. Examination reveals presence of `Mees’ lines in the nails and rain drop pigmentation in the hands. The most likely causative toxin for the above mentioned symptoms is –

**Core Concept**
The patient's presentation of paresthesia, Mees' lines, and raindrop pigmentation is suggestive of arsenic poisoning. Arsenic is a heavy metal that can cause a range of systemic effects, including neurotoxicity, dermatological manifestations, and changes in the nails.

**Why the Correct Answer is Right**
The presence of Mees' lines (white bands on the fingernails) and raindrop pigmentation (hyperpigmented spots on the skin) are classic signs of arsenic toxicity. Arsenic acts by inhibiting the enzyme pyruvate dehydrogenase, leading to cellular energy depletion and ultimately causing cell death. The toxin also interferes with the synthesis of DNA, RNA, and proteins, contributing to its toxic effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Lead poisoning typically presents with abdominal pain, constipation, and peripheral neuropathy, but it does not cause Mees' lines or raindrop pigmentation.
**Option B:** Mercury poisoning can cause neurological symptoms, but it does not typically result in Mees' lines or raindrop pigmentation.
**Option C:** Thallium poisoning can cause hair loss, but it does not characteristically cause Mees' lines or raindrop pigmentation.

**Clinical Pearl / High-Yield Fact**
Mees' lines are a classic sign of heavy metal poisoning, particularly arsenic, and should prompt further investigation for exposure to these toxins.

**Correct Answer:** C. Arsenic.

✓ Correct Answer: B. Arsenic