**Question:** Anti transglutaminase antibodies are seen in

A. Coeliac disease
B. Hashimoto's thyroiditis
C. Sjögren's syndrome
D. Myasthenia gravis

**Core Concept:**
Anti-transglutaminase antibodies are a type of autoantibody that can be found in the blood of patients with certain autoimmune disorders. Transglutaminases are enzymes that play a role in various physiological processes, including tissue remodeling and immune response regulation. There are two main types of transglutaminases: tissue transglutaminase (tTG) and endomysial transglutaminase (eTG).

**Why the Correct Answer is Right:**
Anti-transglutaminase antibodies, particularly anti-tTG, are commonly found in patients with coeliac disease. Coeliac disease is an autoimmune disorder triggered by the consumption of gluten in genetically susceptible individuals. Gluten can damage the small intestine and lead to malabsorption, malnutrition, and other complications. The presence of anti-tTG antibodies, along with other serological markers and clinical findings, can help diagnose coeliac disease.

**Why Each Wrong Option is Incorrect:**

A. Hashimoto's thyroiditis (HT) is an autoimmune disorder that affects the thyroid gland, leading to hypothyroidism. Anti-tTG antibodies are not commonly seen in HT patients, making option A incorrect.

B. Hashimoto's thyroiditis is unrelated to transglutaminase antibodies. Transglutaminase antibodies are more commonly associated with autoimmune conditions affecting the small intestine, such as coeliac disease, than thyroid disorders.

C. Sjögren's syndrome is an autoimmune disorder affecting the exocrine glands, particularly the salivary and lacrimal glands, leading to dryness of the mouth and eyes. Anti-tTG antibodies are not typically seen in Sjögren's syndrome patients.

D. Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction, leading to muscle weakness and fatigue. Anti-tTG antibodies are not associated with MG, making option D incorrect.

**Clinical Pearls:**
In summary, anti-transglutaminase antibodies, particularly anti-tTG, are primarily associated with autoimmune conditions affecting the small intestine, such as coeliac disease. These antibodies can be helpful in diagnosing coeliac disease when combined with clinical findings and serological markers.