Retroauricular Dermatitis: An Orphan Disease

The patient is an 11 year-old girl with a one-year history of a dermatitis in the right retroauricular sulcus.  She has a history of  an eczematous  eruption on her thighs. She was prescribed mupirocin and betamethasone valerate ointmens.  They both caused burning and pruritus and she refused to use them.  There is a history of a vaginal dermatitis a year or so ago, which was successfully treated with topical corticosteroids.

O/E:  There is erythema, crusting and mild fissuring in the above-mentioned area.  The left retorauricular area is mildly affected.  Presently there are no findings of atopic dermatitis in the usual areas.

Clinical Image:

Lab:  Wound culture was positive for 3+ Staph aureus and 3+ Group B Strep.

Diagnosis:  Retroauricular dermatitis.

We prescribed cephalexin 250 mg q.i.d. and a small amount of Vaseline for the dryness and fissuring.  Patch testing will be recommended if there are further symptoms suggestive of contact dermatitis.

Comments:  Retroauricular dermatitis, also called "infra-auricular fissures," appears to be an under-reported entity.  Although it is common in atopic dermatitis, there have been few articles about it. I see a few cases a year and the vast majority yield coagulase positive Staph aureus and occasionally strep when cultured. Most respond quickly to mupirocin ointment and a  low to moderate strength topical steroid.  This patient’s symptoms make her an outlier.  In addition, she has no findings of atopic dermatitis at this time.
Do any of you have thoughts on this entity?  The take home message here is that, as with atopic dermatitis, these lesions are frequently colonized with Staph aureus.

References

1. Infra-auricular fissures in atopic dermatitis.

Tada J, et. al. Acta Derm Venereol. 1994 Mar;74(2):129-31.

Abstract: Retro-auricular or auricular dermatitis in atopic dermatitis (AD) is common and important for the diagnosis of AD in infancy and even in adulthood. Particularly, "infra-auricular fissures", acute eczematous changes like fissures at the adhesive junction of ear lobes, seem to be prominent features for the diagnosis of AD. Of 137 patients with AD, 81.8% showed present or past existence of infra-auricular fissures, but only one of the 30 controls. Of the 46 patients with severe AD, 98% had infra-auricular fissures, compared to 74% in those with moderate and mild AD. Our findings suggest that infra-auricular fissures are important for the diagnosis of AD and should be cited in a list of criteria for the diagnosis of AD.

2. Streptococcal perianal disease in children. Kokx NP, Comstock JA, Facklam RR.  Pediatrics. 1987 Nov;80(5):659-63.  PubMed Link.

3. Psoriasis inversa: A separate identity or a variant of psoriasis vulgaris?

Omland SH, Gniadecki R. Clin Dermatol. 2015 Jul-Aug;33(4):456-61.

Abstract: Psoriasis is a chronic skin disorder affecting approximately 2% of the European and American population. The most common form of psoriasis is the chronic plaque type. Inverse psoriasis, also named flexural or intertriginous psoriasis, is not considered a separate disease entity but rather a special site of involvement of plaque psoriasis, characterized by its localization to inverse/intertriginous/flexural body sites. We review current evidence and establish whether inverse psoriasis is a separate disease entity based on characteristics in terms of epidemiology, pathogenesis, clinical and histologic presentation, microbiology, and treatment.

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