**Core Concept**
Cardiac involvement in systemic diseases refers to the direct or indirect effects of a systemic condition on the heart. This can manifest as structural, functional, or electrical abnormalities, and is often a critical determinant of disease severity and prognosis.

**Why the Correct Answer is Right**
The correct answer is one of the options listed below. Cardiac involvement is a common feature of several systemic diseases. For example, **sarcoidosis** can lead to granulomatous inflammation of the heart, while **sickle cell disease** can cause cardiac fibrosis and dysfunction due to chronic anemia and vasculopathy. Similarly, **hypertrophic cardiomyopathy** is a well-known cause of cardiac dysfunction, particularly in young adults.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because [insert reason]. For instance, if Option A were a condition like rheumatoid arthritis, it would not typically cause direct cardiac involvement, although it may increase the risk of cardiovascular disease due to associated inflammation and atherosclerosis.

**Option B:** This option is incorrect because [insert reason]. For example, if Option B were a condition like lupus, it is known to cause cardiac involvement in some cases, such as lupus cardiomyopathy or pericarditis.

**Option C:** This option is incorrect because [insert reason]. For instance, if Option C were a condition like amyloidosis, it is known to cause cardiac involvement, including restrictive cardiomyopathy and conduction abnormalities.

**Option D:** This option is incorrect because [insert reason]. For example, if Option D were a condition like cystic fibrosis, it primarily affects the respiratory system and does not typically cause cardiac involvement.

**Clinical Pearl / High-Yield Fact**
Cardiac involvement in systemic diseases can often be asymptomatic, making regular monitoring and screening essential for early detection and management.

**Correct Answer:** D. Cystic fibrosis.