**Core Concept**
Pityriasis rotunda is a rare skin condition characterized by circular, oval, or irregular patches of scaling on the trunk and limbs. It is often associated with systemic diseases, malnutrition, and metabolic disorders.

**Why the Correct Answer is Right**
Pityriasis rotunda is a form of pityriasis, which is a group of skin conditions characterized by scaling. The condition is thought to be related to a deficiency in essential fatty acids, leading to abnormalities in lipid metabolism and skin barrier function. The exact pathophysiology is not fully understood, but it is believed to involve impaired fatty acid synthesis and increased peroxisomal fatty acid oxidation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pityriasis rotunda is not a form of eczema or atopic dermatitis.
**Option B:** This option is incorrect because pityriasis rotunda is not primarily associated with viral infections or autoimmune disorders.
**Option C:** This option is incorrect because pityriasis rotunda is not a type of psoriasis or other chronic inflammatory skin disease.

**Clinical Pearl / High-Yield Fact**
Pityriasis rotunda can be associated with systemic diseases, such as diabetes mellitus, liver disease, and malnutrition, and its presence may indicate underlying metabolic disorders. It is essential to consider these systemic conditions when evaluating patients with pityriasis rotunda.

**Correct Answer:** D.