Demodex Folliculorum can Cause Pyogenic Granuloma of Conjunctiva

Abstract

An elderly Caucasian female with a history of oral lichen planus and functional nasolacrimal obstruction underwent bilateral Dacryocystorhinostomy (DCR). Eight months later tearing symptoms recurred, right greater than left, and a right lower medial eyelid inflammatory process was clinically correctly diagnosed as pyogenic granuloma. Excision and drainage without pathology was performed but the inflammation continued despite topical therapy with steroids and antibiotics. Clinical suspicion of conjunctival lichen planus prompted serial topical mitomycin-C applications effecting slight improvement over six-months. Persistence of the lesion led to a biopsy initially interpreted as pyogenic granuloma and subsequent step-sections of the specimen demonstrated a cyst containing probable parasite debris. A second deeper biopsy three months later revealed only granulation tissue. Thereafter the problematic area gradually healed. Controversy as to what parasite was responsible prompted a Center for Disease Control consult resulting in an unexpected diagnosis of Demodex folliculorum. Methods: We reviewed all clinical and pathology records related to this case. She had not traveled out of her home area or visited any agricultural fair or farm and did not remember any insect bites. Results: Parasitic debris was initially thought consistent with the external cuticle of a fly larva such as Oestrus Ovis [Sheep bot fly]. Eventual consultation with the Center for Disease Control resulted in a diagnosis of inflammation residual to Demodex folliculorum migration into conjunctival stroma. Conclusion: Persisting conjunctival inflammation can be due to Demodex folliculorum stromal invasion to locations far from eyelid skin, the common site of mite infestation.