**Question:** Pleurisy is common in which one of the following connective tissue diseases:

A. Systemic Sclerosis (Scleroderma)
B. Systemic Lupus Erythematosus (SLE)
C. Rheumatoid Arthritis
D. Polymyositis/Dermatomyositis (PM/DM)

**Core Concept:**
Pleurisy refers to inflammation of the pleura, the thin, fibrous lining that surrounds the lungs and forms the chest wall. In the context of connective tissue diseases, we are considering the relationship between pleurisy and the four mentioned disorders. Connective tissue diseases are a group of conditions characterized by inflammation and damage to connective tissue, which is essential for maintaining the structure and function of organs and tissues.

**Why the Correct Answer is Right:**
Pleurisy is indeed common in certain connective tissue diseases. Among the options provided, the correct answer is **D.** Polymyositis/Dermatomyositis (PM/DM). PM/DM are a group of autoimmune diseases characterized by inflammation and muscle weakness. The inflammation in PM/DM is primarily focused on the muscles and skin, hence the name, but it can also lead to pleural involvement. The pleural inflammation may present as pleurisy, causing symptoms like chest pain, fever, and sometimes, pleural effusion (fluid accumulation in the pleural space).

**Why Each Wrong Option is Incorrect:**
A. **Systemic Sclerosis (Scleroderma)** is a disease characterized by excessive collagen deposition, affecting not only the skin but also internal organs. Pleurisy is relatively uncommon in this disorder.

B. **Systemic Lupus Erythematosus (SLE)** is an autoimmune disease with wide-ranging manifestations, but pleurisy is not a common manifestation of SLE.

C. **Rheumatoid Arthritis** is primarily characterized by joint inflammation, making it unlikely to cause pleurisy. Pleurisy is a consequence of systemic inflammation in other conditions.

**Clinical Pearl:**
While the correct answer (PM/DM) is an autoimmune disorder, it is essential to differentiate between connective tissue diseases, autoimmune disorders, and specific manifestations of pleurisy. Connective tissue diseases include systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, and polymyositis-dermatomyositis. Autoimmune disorders are a broader category that includes these connective tissue diseases along with other conditions where the immune system attacks the body's own cells or tissues, leading to inflammation and damage. Polymyositis-dermatomyositis (PM/DM) is an autoimmune disorder affecting skeletal muscles and skin, which can lead to pleural inflammation and pleurisy.