**Question:** Bald tongue of Sandwith is seen in

A. Angiodysplasia
B. Lichen planus
C. Acquired immunodeficiency syndrome (AIDS)
D. Vitamin B12 deficiency

**Correct Answer:** D. Vitamin B12 deficiency

**Core Concept:**

Bald tongue, also known as macroglossia, refers to the enlargement of the tongue due to increased thickness and prominence of the lingual papillae. It is a clinical sign that can indicate various underlying pathological conditions. Bald tongue of Sandwith is particularly associated with vitamin B12 deficiency.

**Why the Correct Answer is Right:**

Vitamin B12, also known as cobalamin, plays a crucial role in the maintenance of normal nerve function and DNA synthesis in rapidly dividing cells. It is involved in the regulation of cell division, myelination, and blood cell production. In the context of the tongue, vitamin B12 deficiency results in macroglossia due to the disruption of normal tongue structure and function.

**Why Each Wrong Option is Incorrect:**

A. Angiodysplasia is a vascular malformation of the gastrointestinal tract, characterized by dilated and tortuous blood vessels. It is not the cause of macroglossia but can be associated with iron deficiency anemia.

B. Lichen planus is a chronic inflammatory disease affecting skin, mucous membranes, and nails. It is not linked to macroglossia but rather presents with mucosal lesions and skin changes.

C. Acquired immunodeficiency syndrome (AIDS) is a viral infection caused by HIV (Human Immunodeficiency Virus). It is a syndrome affecting the immune system and is not directly associated with macroglossia. AIDS patients may present with other oral manifestations, but macroglossia is not a common finding.

**Clinical Pearl:**

Bald tongue can be a diagnostic clue for vitamin B12 deficiency. In addition to macroglossia, other symptoms and signs of vitamin B12 deficiency include pallor, fatigue, and impaired cognitive function. A comprehensive evaluation should be performed to identify the cause of vitamin B12 deficiency, which may include a blood test for serum vitamin B12 levels and a stool for methylmalonic acid and homocysteine levels. Treatment involves vitamin B12 replacement therapy.

When examining patients presenting with macroglossia, it is essential to consider the possibility of vitamin B12 deficiency, particularly in the context of other clinical findings and patient history. Early recognition and treatment can prevent neurological complications associated with vitamin B12 deficiency.