Okay, I need to figure out which vitamin deficiency causes glossitis and cheilitis. Let's start by recalling what these conditions are. Glossitis is inflammation of the tongue, often leading to a smooth, red, and sore tongue. Cheilitis is inflammation of the lips, which can cause cracking, redness, and scaling.

Now, vitamins that are commonly associated with these symptoms. Let me think. B vitamins are a big category here. For example, B2 (riboflavin) deficiency can cause angular cheilitis and a sore, red tongue. B3 (niacin) deficiency leads to pellagra, which includes dermatitis, diarrhea, and dementia. B12 deficiency can cause glossitis as well, but maybe not cheilitis. B6 deficiency can also lead to glossitis and cheilosis.

Wait, the question is asking for both glossitis and cheilitis. So which one is the most common? Angular cheilitis is often linked to B2. Another possibility is B6. Let me check. Riboflavin deficiency specifically is known for angular cheilitis and glossitis. So maybe the answer is B2. Let me confirm. Yes, riboflavin deficiency (B2) is a classic cause of these symptoms. B6 can also cause similar issues but maybe not as classically. B12 might cause glossitis but not cheilitis. So the correct answer is B2 deficiency.

**Core Concept**
Glossitis (inflammation of the tongue) and cheilitis (inflammation of the lips) are classic signs of **B vitamin deficiencies**, particularly **B2 (riboflavin)**, **B6 (pyridoxine)**, and **B12 (cobalamin)**. These vitamins are critical for maintaining mucosal integrity and redox reactions.

**Why the Correct Answer is Right**
**Riboflavin (B2)** deficiency causes **angular cheilitis** (cracking at the corners of the mouth) and **glossitis** due to impaired epithelial cell function and oxidative stress. Riboflavin is a precursor for flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are cofactors in energy metabolism and antioxidant defense. Deficiency disrupts mucosal barrier integrity, leading to inflammation.

**Why Each Wrong Option is Incorrect**
**Option A:** **Vitamin B12 deficiency** causes glossitis but not cheilitis. It primarily leads to megaloblastic anemia, neurological symptoms, and a "beefy red tongue."
**Option B:** **Vitamin B6 deficiency** causes glossitis and cheilosis (inflamed lips) but is less classically associated with angular cheilitis compared to B2.
**Option D:** **Vitamin B1 (thiamine)** deficiency causes beriberi (neuropathy, heart failure) and Wernicke encephalopathy, not oral lesions.

**Clinical Pearl / High-Yield Fact**
**"B2 cracks the corners, B12 paints the tongue red."** Angular cheilitis is a hallmark of riboflavin deficiency. Remember the "3 Cs" of B2 deficiency: **Cheilosis**, **Cracks at corners of mouth**, and **

✓ Correct Answer: A. Vit. B2