Which of the following is an autoimmune disease?

Options

A. Rheumatoid arthritis
B. Asthma
C. Diphtheria
D. SCID

Answer

To determine which of the following options is an autoimmune disease, we need to analyze each option based on the definition of autoimmune diseases. An autoimmune disease occurs when the immune system mistakenly attacks the body's own healthy cells.

### Step-by-Step Solution:

1. **Understand Autoimmune Diseases**:
- Autoimmune diseases are conditions where the immune system attacks healthy cells instead of foreign pathogens.

2. **Evaluate the Options**:
- **Option 1: Rheumatoid Arthritis**:
- This is a chronic inflammatory disease that primarily affects the joints.
- The immune system attacks the synovium (the lining of the joints), leading to inflammation, pain, and potential deformity.
- **Conclusion**: Rheumatoid arthritis is indeed an autoimmune disease.

- **Option 2: Asthma**:
- Asthma is an allergic reaction that affects the airways, leading to difficulty in breathing.
- It is primarily caused by allergens and is not a condition where the immune system attacks the body’s own cells.
- **Conclusion**: Asthma is not an autoimmune disease.

- **Option 3: Diphtheria**:
- Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae.
- It leads to respiratory issues but is not related to the immune system attacking healthy cells.
- **Conclusion**: Diphtheria is not an autoimmune disease.

- **Option 4: SCID (Severe Combined Immunodeficiency)**:
- SCID is a genetic disorder that results in a severely compromised immune system.
- It is caused by mutations affecting the development of immune cells, making individuals highly susceptible to infections.
- **Conclusion**: SCID is not an autoimmune disease.

3. **Final Answer**:
- Based on the evaluations, the only autoimmune disease among the options provided is **Rheumatoid Arthritis**.