**Core Concept**
Anhidrosis, or the inability to sweat, can be caused by various factors affecting the eccrine glands, which are responsible for thermoregulation and electrolyte balance. This condition can arise from damage to the sympathetic nervous system, certain medications, or underlying diseases affecting the skin or nervous system.

**Why the Correct Answer is Right**
The correct answer is related to anhidrosis caused by damage to the sympathetic nervous system, specifically the postganglionic fibers that innervate the eccrine glands. This is because eccrine glands are cholinergically innervated, and their function is regulated by the sympathetic nervous system. The absence of postganglionic fibers leads to impaired eccrine gland function and anhidrosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anhidrosis can be caused by various factors, including certain medications, underlying diseases, or damage to the eccrine glands themselves, not just the sympathetic nervous system.

**Option B:** This option is incorrect because anhidrosis can be caused by damage to the sympathetic nervous system, including preganglionic fibers, which are involved in the parasympathetic nervous system, and postganglionic fibers.

**Option C:** This option is incorrect because anhidrosis can be caused by damage to the sympathetic nervous system, including the postganglionic fibers that innervate the eccrine glands.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that anhidrosis can be a sign of underlying neurological or dermatological conditions, such as Horner's syndrome, diabetes mellitus, or Sjögren's syndrome. A thorough medical history and physical examination are crucial in diagnosing the underlying cause of anhidrosis.

**Correct Answer: D**