**Core Concept**
The patient's symptoms suggest a condition affecting the neuromuscular junction, characterized by descending paralysis, areflexia, and non-reactive pupils. This is a classic presentation of a condition caused by an autoimmune response against the acetylcholine receptor.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with myasthenia gravis (MG), an autoimmune disorder that results from antibodies targeting the acetylcholine receptor (AChR) at the neuromuscular junction. This leads to a decrease in the number of functional AChR, causing a reduction in acetylcholine-mediated muscle contraction. The blurring of vision is likely due to involvement of the extraocular muscles, which are also affected by the autoimmune response. The non-reactive pupils are a result of the involvement of the ciliary muscles, which are also innervated by the autonomic nervous system and have AChR.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might suggest Guillain-Barré syndrome, which is an autoimmune disorder that affects the peripheral nerves. However, Guillain-Barré syndrome typically presents with ascending paralysis and often has a preceding infection.

**Option B:** This option might suggest botulism, a condition caused by a toxin that blocks acetylcholine release at the neuromuscular junction. However, botulism typically presents with descending paralysis, but it also has a history of food poisoning or contaminated food, which is not mentioned in the patient's history.

**Option C:** This option might suggest Lambert-Eaton myasthenic syndrome (LEMS), another autoimmune disorder that affects the neuromuscular junction. However, LEMS typically presents with proximal muscle weakness, autonomic dysfunction, and often has a preceding cancer diagnosis.

**Option D:** This option might suggest spinal cord injury or compression, which can cause quadriparesis and areflexia. However, the patient's symptoms, including the history of blurring of vision and non-reactive pupils, do not suggest a spinal cord lesion.

**Clinical Pearl / High-Yield Fact**
Myasthenia gravis is often associated with thymic abnormalities, particularly thymoma, and can also be associated with other autoimmune disorders, such as thyroiditis and rheumatoid arthritis. A high index of suspicion is required to diagnose MG, as the symptoms can be subtle and variable.

**Correct Answer:** C.