**Core Concept**
The mucosa is a layer of epithelial tissue lining the internal surfaces of the body, including the respiratory, gastrointestinal, and genitourinary tracts. Involvement of the mucosa can occur due to various factors such as inflammation, infection, or trauma.

**Why the Correct Answer is Right**
The correct answer involves a condition where the mucosa is not directly affected, as it is primarily a disease of the deeper tissues. The mucosa may be involved in secondary reactions, such as inflammation or scarring, but it is not the primary site of pathology. This condition is characterized by the involvement of the synovial membrane and the deeper tissues of the joint, leading to joint pain and swelling.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because mucosal involvement is a hallmark of this condition, leading to symptoms such as coughing and wheezing.
**Option B:** This option is incorrect because mucosal inflammation is a key feature of this disease, leading to symptoms such as diarrhea and abdominal pain.
**Option C:** This option is incorrect because mucosal involvement is a common complication of this condition, leading to symptoms such as oral thrush and vaginal yeast infections.

**Clinical Pearl / High-Yield Fact**
This condition is often referred to as a "silent disease" because it can progress without symptoms for a long time, until the joint is severely damaged.

**Correct Answer: D. Rheumatoid Arthritis.