Ectoparasite Bite

July 19, 2012

This was presumed to be an ectoparasite bite when the patient reported that she had a new pet kitten. A myriad of diagnostic possibilities exist, including the start of a drug eruption or viral infection, early allergic contact dermatitis, or first manifestation of an autoimmune bullous disease.

A 26-year-old woman presented with 2 extremely pruritic lesions on the upper back. Ipsilateral axillary adenopathy was absent, and she was otherwise in good health.

Key point: The lesions consist of subtle erythema and edema with a small central vesicle. A myriad of diagnostic possibilities exist. This could be the start of a drug eruption or viral infection. It could represent insect bites or stings. An early allergic contact dermatitis or the first manifestation of an autoimmune bullous disease could present in this manner. In this instance, history becomes very important. The patient has a new pet kitten, and after a KOH preparation was negative, this was presumed to be an ectoparasite bite.

Treatment: Topical 1% hydrocortisone relieved itching and hastened involution.

Note:Cheyletiella mites were discovered on the kitten by the family’s veterinarian.