Dennie morgan fold is seen in –
**Core Concept**
The Dennie-Morgan fold is a visible skin fold under the lower eyelid, typically indicative of atopic conditions such as allergic rhinitis or asthma. It is caused by the thickening of the subcutaneous tissue and the orbicularis oculi muscle due to chronic inflammation and edema.
**Why the Correct Answer is Right**
The Dennie-Morgan fold is a clinical sign that aids in the diagnosis of atopic conditions. The pathophysiology involves the chronic inflammation and edema of the subcutaneous tissue and the orbicularis oculi muscle, leading to the formation of a visible skin fold under the lower eyelid. This is a result of the body's allergic response and the subsequent release of histamine and other chemical mediators.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the Dennie-Morgan fold is not typically associated with conjunctivitis.
**Option B:** This option is incorrect as the Dennie-Morgan fold is not a characteristic feature of thyroid ophthalmopathy.
**Option C:** This option is incorrect as the Dennie-Morgan fold is not a common finding in blepharospasm.
**Clinical Pearl / High-Yield Fact**
The Dennie-Morgan fold is a high-yield clinical sign that can aid in the diagnosis of atopic conditions, particularly allergic rhinitis and asthma. It is essential to recognize this sign in patients presenting with symptoms of these conditions.
**Correct Answer:** C.