**Core Concept**
Autoimmune diseases are characterized by the immune system mistakenly attacking and damaging healthy tissues and organs, leading to chronic inflammation and tissue destruction. This occurs due to a loss of tolerance to self-antigens, resulting in the production of autoantibodies and activation of autoreactive T cells.

**Why the Correct Answer is Right**
All of the options listed (Sjogren's syndrome, Mikulicz's disease, and Rheumatoid arthritis) are classic examples of autoimmune diseases. Sjogren's syndrome is an autoimmune disorder that primarily affects the exocrine glands, particularly the salivary and lacrimal glands, leading to dry mouth and dry eyes. Mikulicz's disease is a rare autoimmune disorder characterized by the enlargement of the salivary and lacrimal glands, often associated with Sjogren's syndrome. Rheumatoid arthritis is a systemic autoimmune disease that primarily affects the joints, leading to inflammation, pain, and deformity. The pathophysiology of these diseases involves the production of autoantibodies and activation of autoreactive T cells, which contribute to chronic inflammation and tissue damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Although Sjogren's syndrome is an autoimmune disease, this option only partially answers the question.

**Option B:** While Mikulicz's disease is associated with autoimmune processes, it is not a standalone autoimmune disease.

**Option C:** Although Rheumatoid arthritis is an autoimmune disease, this option only partially answers the question.

**Clinical Pearl / High-Yield Fact**
Autoimmune diseases often have a strong association with genetic predisposition, with certain genetic variants contributing to the development of autoimmunity. It is essential for clinicians to consider the patient's medical history, family history, and laboratory findings when diagnosing autoimmune diseases.

**✓ Correct Answer: D. All of the above.**