This is diagnosed by the presence of a type of IgM

Options

A. Osteoporosis
B. Gout
C. Osteoarthritis
D. Rheumatoid arthritis

Answer

To determine which disorder is diagnosed by the presence of a type of IgM, we can analyze the options provided:

1. **Osteoporosis**: This is primarily an age-related condition that affects bone density, particularly in postmenopausal women. It is not an immune system-related disorder. Therefore, it does not involve IgM.

2. **Gout**: Gout is characterized by the inflammation of joints due to the accumulation of uric acid crystals. This condition is related to metabolic issues rather than the immune system. Thus, it does not involve IgM.

3. **Osteoarthritis**: This is another form of joint inflammation that can arise from various factors, including wear and tear on the joints. Like the previous conditions, osteoarthritis is not an autoimmune disorder and does not involve IgM.

4. **Rheumatoid Arthritis**: This is an autoimmune disorder where the body mistakenly attacks its own tissues, particularly the synovial tissue in the joints. In rheumatoid arthritis, the presence of IgM antibodies, specifically rheumatoid factor (RF), is a key diagnostic marker. Thus, this condition is indeed associated with IgM.

Based on the analysis, the correct answer is **Rheumatoid Arthritis**, which is diagnosed by the presence of IgM.

### Step-by-Step Solution:
1. **Identify the types of disorders listed**: Osteoporosis, Gout, Osteoarthritis, and Rheumatoid Arthritis.
2. **Evaluate each disorder**:
- Osteoporosis: Age-related, not immune-related.
- Gout: Caused by uric acid crystals, not immune-related.
- Osteoarthritis: Joint inflammation, not autoimmune.
- Rheumatoid Arthritis: Autoimmune disorder, associated with IgM.
3. **Determine the correct disorder**: Rheumatoid Arthritis is the only condition that involves the presence of IgM.