**Core Concept**
Tetanus is a neurotoxin-mediated disease caused by Clostridium tetani, which affects the nervous system by releasing tetanospasmin. This toxin interferes with neurotransmitter release, particularly inhibitory neurotransmitters like glycine and GABA, leading to excessive muscle contraction and rigidity.

**Why the Correct Answer is Right**
The correct answer relates to the pathophysiology of tetanus, where tetanospasmin blocks the release of inhibitory neurotransmitters from the presynaptic neuron. This results in an imbalance between excitatory and inhibitory neurotransmission, leading to the characteristic muscle spasms and rigidity associated with tetanus. Tetanospasmin specifically inhibits the release of glycine and GABA from the inhibitory neurons, which are essential for regulating muscle tone and preventing excessive contraction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because tetanus is not caused by a deficiency of tetanospasmin. Tetanospasmin is the toxin responsible for the disease, and its presence is what leads to the characteristic symptoms.

**Option B:** This option is incorrect because tetanus is not primarily an autoimmune disease. While the immune response may play a role in the disease, the primary mechanism of action is through the neurotoxin tetanospasmin.

**Option C:** This option is incorrect because tetanus is not caused by an imbalance of calcium and potassium ions. While these ions are involved in muscle contraction, the primary mechanism of tetanus is through the action of tetanospasmin on inhibitory neurotransmitters.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of tetanus is the presence of muscle rigidity, particularly in the jaw (lockjaw) and abdominal muscles, which can lead to respiratory failure if left untreated. The disease is characterized by a triad of muscle rigidity, spasms, and autonomic dysfunction.

**Correct Answer:** Not provided