Selenosis — Chronic consumption of excess selenium most commonly leads to which clinical manifestation?

Introduction / Context:
Selenium is a trace element with a narrow safe intake range. While deficiency has health risks, chronic excess (selenosis) produces characteristic toxicity signs. This question asks you to identify the hallmark presentation associated with long-term high selenium intake.

Given Data / Assumptions:

• Selenium participates in selenoproteins (e.g., glutathione peroxidases, thioredoxin reductases).
• Toxicity depends on chemical form and cumulative exposure.
• Clinical features of excess are relatively distinctive.

Concept / Approach:
Classic selenosis symptoms include brittle hair and nails (which may break or fall out), garlic-like breath odor (volatile selenium compounds), gastrointestinal upset, fatigue, irritability, and peripheral neuropathy in more severe cases. The most commonly taught distinctive sign is brittle hair and nails, frequently queried in examinations.

Step-by-Step Solution:

Verification / Alternative check:
Environmental and supplement-related outbreaks document nail and hair changes as early markers of selenosis; reducing intake reverses findings over weeks to months.

Why Other Options Are Wrong:

• Muscle weakness/diarrhea: can occur but are less specific than the hallmark integumentary signs.
• TPN: a therapy, not a symptom; if selenium is omitted, it causes deficiency, not toxicity.
• Photosensitivity rash: not a classic selenosis sign.

Common Pitfalls:
Confusing selenium excess with deficiency manifestations such as cardiomyopathy (Keshan disease) or impaired immunity; these reflect low, not high, selenium status.

Final Answer:
brittle hair and nails.