**Core Concept**
Sensory-motor neuropathy refers to a type of peripheral neuropathy that affects both sensory and motor nerve fibers, leading to a combination of sensory deficits and muscle weakness. This condition can result from various causes, including metabolic disorders, toxic exposures, and infectious diseases.

**Why the Correct Answer is Right**
Sensory-motor neuropathy is a common complication of diabetes mellitus (DM). The underlying mechanism involves hyperglycemia-induced oxidative stress, which causes damage to the myelin sheath and axons of peripheral nerve fibers. This leads to a decrease in nerve conduction velocity and ultimately results in sensory and motor deficits. The involvement of both sensory and motor nerves is characteristic of this type of neuropathy.

**Why Each Wrong Option is Incorrect**
* **Option B:** Lead poisoning primarily causes a motor neuropathy, characterized by weakness and atrophy of muscles, particularly in the extremities. Sensory involvement is less common.
* **Option C:** Arsenic exposure is associated with a sensory neuropathy, characterized by pain, numbness, and tingling in the hands and feet. Motor involvement is not a prominent feature.
* **Option D:** Leprosy (Hansen's disease) can cause a mixed sensory and motor neuropathy, but it is not as common as in diabetic patients. Leprosy primarily affects the skin and peripheral nerves, leading to sensory loss and muscle weakness.
* **Option E:** AIDS (Acquired Immunodeficiency Syndrome) can cause a variety of neurological complications, including peripheral neuropathy. However, the type of neuropathy associated with AIDS is more often a distal sensory neuropathy, characterized by pain, numbness, and tingling in the hands and feet.

**Clinical Pearl / High-Yield Fact**
Diabetic patients with sensory-motor neuropathy may present with a characteristic "glove and stocking" distribution of sensory deficits, with decreased sensation to light touch, pinprick, and temperature. Early recognition and management of diabetes are crucial in preventing the development of this debilitating condition.

**Correct Answer: A. Diabetes Mellitus**