Which of the following disorders is characterised by rapid spasm in muscles due to lack of Ca in body fluids?

Options

A. Tetany
B. Muscle atrophy
C. Muscular dystrophy
D. Myasthenia gravis

Answer

To solve the question regarding which disorder is characterized by rapid spasms in muscles due to a lack of calcium in body fluids, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a disorder that involves rapid muscle spasms caused by a deficiency of calcium in the body fluids.

2. **Identifying Key Terms**:
- "Rapid spasm in muscles" indicates involuntary muscle contractions.
- "Lack of Ca" refers to a deficiency of calcium.

3. **Reviewing Possible Disorders**:
- **Tetany**: This condition is characterized by muscle spasms and cramps due to low levels of calcium in the blood. It is directly linked to calcium deficiency.
- **Muscle Atrophy**: This refers to the wasting away of muscle tissue, usually due to lack of use or physical activity, not calcium deficiency.
- **Muscular Dystrophy**: A genetic disorder that leads to progressive muscle weakness and loss of muscle mass, not specifically related to calcium levels.
- **Myasthenia Gravis**: An autoimmune disorder that affects communication between nerves and muscles, leading to weakness and fatigue, but not directly related to calcium deficiency.

4. **Conclusion**: Based on the definitions and characteristics of the disorders, tetany is the only condition that matches the description of rapid muscle spasms due to a lack of calcium in body fluids.

5. **Final Answer**: The correct answer is **Tetany**.