**Core Concept**
Myositis ossificans progressive, also known as Fibrodysplasia ossificans progressiva (FOP), is a rare and disabling genetic disorder characterized by the abnormal formation of bone within soft tissues, including muscles, tendons, and ligaments. This progressive condition leads to ankylosis (fusion) of joints and eventually confines the patient to a wheelchair.

**Why the Correct Answer is Right**
The most probable cause of death in patients with FOP is respiratory failure due to progressive ankylosis of the chest wall and diaphragm, which severely restricts lung expansion and compromises gas exchange. As the disease advances, patients experience increasing difficulty breathing, leading to respiratory failure, which is often the primary cause of mortality. The chest wall and diaphragmatic ankylosis also predisposes patients to pneumonia and respiratory infections, further complicating their clinical course.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while cardiac complications can occur in patients with FOP, they are not the most probable cause of death. Cardiac issues are more commonly seen in conjunction with respiratory failure.

**Option B:** This option is incorrect because there is no established link between FOP and gastrointestinal complications as the primary cause of death.

**Option C:** This option is incorrect because while infections can be a significant concern in patients with FOP, they are not the most probable cause of death.

**Clinical Pearl / High-Yield Fact**
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder that should be considered in patients with a history of recurrent heterotopic ossification, especially if there is a family history of the condition. Early recognition and management are crucial to improving patient outcomes and quality of life.

**Correct Answer:** C. Respiratory failure.