A patient recently presented with a subcutaneous nodule that appeared to be an abscess. It was raised, erythematous, tender, indurated, and had a central plug…wait, no, it had a central hole. And he just got back from Belize. We put a transparent membrane on it to see if there was a creature in there. Sure enough, a snout pushed at the membrane, seeking air. This established the diagnosis – myiasis, secondary to a bot fly bite.
Trying to remove that larvae was an ordeal. These creatures don’t want to leave their cubby, and trying to pull them out is like trying to give a cat a bath. We finally decided to leave the membrane in place. The next morning the larva was dead, and my colleague removed it.
Other skin lesions that can be confused with an abscess include a brown recluse bite. Reportedly a blue lesion, surrounded by concentric rings of pallor (ischemia) and then erythema (vasodilation) are classic for the brown recluse bite (Rogers 2011).