Classification – Odd one out (deficiency diseases vs infectious disease): Which is different from the rest: Scurvy, Rickets, Night-blindness, Influenza?

Introduction / Context:
The list mixes medical conditions of two fundamentally different etiologies. Three are classical vitamin deficiency disorders. One is an infectious viral illness. Identify the one that is not a deficiency disease.

Given Data / Assumptions:

• Scurvy — deficiency of vitamin C.
• Rickets — deficiency of vitamin D (and/or calcium/phosphate abnormalities), leading to bone demineralization in children.
• Night-blindness — commonly due to vitamin A deficiency (nyctalopia).
• Influenza — acute infectious disease caused by influenza viruses (A/B/C), not a vitamin deficiency.

Concept / Approach:
Group conditions by cause: “vitamin deficiency” vs “pathogen infection.” Scurvy, Rickets, Night-blindness share the deficiency cause; Influenza is viral. Hence, Influenza is the outlier.

Step-by-Step Solution:
1) Tag etiologies: Scurvy/Rickets/Night-blindness → deficiency; Influenza → viral infection.2) Pick the single viral disease as the odd one: Influenza.

Verification / Alternative check:
Consider prevention: dietary correction/supplementation remedies deficiency diseases; vaccination and hygiene practices target influenza transmission. Different prevention paradigms confirm different categories.

Why Other Options Are Wrong:
They are all deficiency conditions tied to specific vitamins.

Common Pitfalls:
Assuming “night-blindness” is generic—exam convention treats it as vitamin A deficiency unless specified otherwise.

Final Answer:
Influenza