Diagnosis: Infectious eczematoid dermatitis
The patient was referred to a dermatologist after seeing an ear, nose, and throat (ENT) specialist who made the diagnosis of otitis externa when the rash failed to respond to topical and systemic antibiotics. The patient’s tender, pruritic, oozing, edematous eruption was recognized as an infectious eczematoid dermatitis (IED).
Although it is not an uncommon condition, IED may be underrecognized. It accounted for 2.9% of admissions to a dermatology-run inpatient service between 2000 and 2010.1 IED results from cutaneous sensitization to purulent drainage secondary to acute otitis externa or another primary infection.2 In fact, cultures from the purulent drainage in this patient grew methicillin-resistant Staphylococcus aureus. The patient’s right otitis externa drainage may have been associated with the previous history of atopic dermatitis. Atopic dermatitis is associated with an increased risk of skin infections due to decreased inflammatory mediators (defensins).
Cellulitis and herpes zoster oticus are part of the differential
The differential diagnosis in this case includes bacterial cellulitis, acute otitis media, and herpes zoster oticus.
Bacterial cellulitis manifests with erythema, edema, and tenderness with blistering when associated with bullous impetigo rather than pruritus. The clinical appearance of the patient’s diffuse, weeping, edematous external ear, the lack of response to guided antibiotic therapy, and the pruritus experienced by the patient argue against the diagnosis of bacterial cellulitis.
Acute otitis media, like otitis externa, produces ear discharge usually associated with significant pain. Thus, it is important when working through the differential to define the source of the ear discharge. In this case, a consultation with an ENT specialist confirmed that there was an intact tympanic membrane with no middle ear involvement, ruling out the diagnosis of acute otitis media.
Continue to: Herpes zoster oticus