**Core Concept**
Calabar swellings are a characteristic skin manifestation of Loa loa filariasis, a parasitic infection caused by the Loa loa worm. These swellings are a result of the worm's migration through the subcutaneous tissue, causing localized inflammation and edema.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of Loa loa filariasis. When the Loa loa worm migrates through the subcutaneous tissue, it can cause localized inflammation and edema, leading to the formation of Calabar swellings. This is due to the immune response to the worm, which involves the activation of inflammatory cells and the release of various cytokines and mediators that contribute to the edema.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Calabar swellings are not typically seen in onchocerciasis, a different parasitic infection caused by Onchocerca volvulus.
**Option B:** This option is incorrect because Calabar swellings are not a characteristic feature of lymphatic filariasis, which is caused by different species of filarial worms such as Wuchereria bancrofti and Brugia malayi.
**Option C:** This option is incorrect because Calabar swellings are not a feature of schistosomiasis, a parasitic infection caused by Schistosoma species.

**Clinical Pearl / High-Yield Fact**
It's essential to note that Calabar swellings are often seen in patients with Loa loa filariasis, particularly in areas where the disease is endemic, such as in central Africa. The presence of these swellings can be a diagnostic clue for Loa loa filariasis.

**Correct Answer: D. Loa loa filariasis.**