"Demodicosis" Mimicking PreSeptal Cellulitis: Severe Periocular and Facial Inflammation Caused by "Normal" Skin Flora

Due to their relatively high prevalence and commensalism, the pathogenicity of Demodex mites has been debated. Recent data, however, show Demodex to be associated with skin and ocular surface diseases such as rosacea, blepharitis, and keratitis. Here the authors report the first known case, to the best of the their knowledge, of Demodex infestation mimicking preseptal cellulitis in an adult human. A 29-year-old male bilaterally blind from advanced retinopathy of prematurity presented with a 2-month history of right-greater-than-left upper eyelid and periocular/cheek swelling, redness, and ocular discharge that did not resolve with oral antibiotics or oral steroids. Based on MRI findings, biopsies of the right lacrimal gland, right orbital fat, and right upper eyelid preseptal skin were obtained which revealed marked intrafollicular Demodex mite density and budding yeasts in the upper eyelid skin. This case serves to alert clinicians to this entity that may not otherwise be usually considered in ophthalmic clinical practice.