**Core Concept**
Polyarteritis nodosa (PAN) is a medium vessel vasculitis characterized by inflammation and necrosis of the blood vessel walls, leading to various systemic manifestations, including skin involvement. The skin manifestations of PAN are a result of the direct effect of the inflammatory process on the skin and its underlying structures.

**Why the Correct Answer is Right**
Skin manifestations of PAN are a result of the inflammation of the small and medium-sized blood vessels, which can lead to ischemia and infarction of the skin. One of the characteristic skin manifestations of PAN is the presence of subcutaneous infarcts, which occur due to the occlusion of the small blood vessels supplying the skin. This can result in the formation of painful subcutaneous nodules or infarcts.

**Why Each Wrong Option is Incorrect**
**Option A:** Livido reticularis is more commonly associated with conditions such as meningococcemia and other severe infections, where there is a profound vasodilation and increased permeability of the blood vessels, leading to a characteristic reticular or lace-like pattern on the skin. This is not a typical feature of PAN.
**Option B:** Hyperpigmentation can occur in various dermatological conditions, but it is not a characteristic skin manifestation of PAN.
**Option C:** Bullous dermatitis is not a typical skin manifestation of PAN. The skin manifestations of PAN are more commonly characterized by necrotic lesions, subcutaneous infarcts, or livedo reticularis.

**Clinical Pearl / High-Yield Fact**
The skin manifestations of PAN can be distinguished from other forms of vasculitis by the presence of subcutaneous infarcts, which are typically painful and have a characteristic appearance on imaging studies.

**Correct Answer:** C. Subcutaneous infarct