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DERMATOLOGY DIGEST

A derm photo quiz

LT Kenneth J. Meehan, PA-C, MPAS,
DEPARTMENT EDITOR

A persistent auricular rash in a 12-year-old girl

Joe R. Monroe, PA-C, MPAS

Mr. Monroe practices in the dermatology department of the Springer Clinic, Tulsa, Okla, and is the founder and president-elect of the Society of Dermatology Physician Assistants. The author has indicated no relationships to disclose relating to the content of this article. Lieutenant Meehan practices dermatology at Tripler Army Medical Center, Honolulu, Hawaii.

A 12-year-old girl was referred for evaluation of a slightly itchy rash that had been present in both external ears for more than 2 years. She was treated with several prescription and OTC medications—including 1% hydrocortisone cream, miconazole cream, and terbinafine cream (Lamisil)—none of which did the slightest bit of good. She was also treated with oral fluconazole (Diflucan) and tea tree oil, again without success.

The patient had a family history of psoriasis, but she and the family said that her rash had not affected the scalp, elbows, or knees. The patient had no joint pain, and the family specifically denied a history of atopy.

Examination of the affected areas revealed a rather thick, tenacious, white scale uniformly covering most of both external auditory meatus (see Figure 1). The rash, which was salmon pink in color, extended only a centimeter or so into the ear canals and then stopped abruptly. A faint but similar rash was noted behind both ears. The patient's elbows, knees, and scalp appeared normal, but examination of her fingernails showed several discrete pits. A potassium hydroxide (KOH) examination of the ear scale was negative for fungal elements.

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What is your diagnosis?

Atopic dermatitis
Seborrheic dermatitis
Psoriasis

Discussion

The correct answer is psoriasis. Even though this condition typically affects extensor surfaces such as elbows and knees, it quite commonly appears in only one area, such as the scalp, nails, or ears. In this patient, the micaceous white scaling in and around the ears, the negative KOH test, the nail pits, and the positive family history combined to make a fairly persuasive case for the diagnosis of psoriasis. If treatment for psoriasis had failed or if some of these findings had been absent, a punch biopsy could have been done to definitively establish the diagnosis. However, given that common conditions occur as commonly as they do and that psoriasis affects almost 3% of the white population, one would expect to see it with some regularity.

Atopic dermatitis, unlike psoriasis, seldom affects only one area and instead would also have been seen on areas such as the arms or neck at some point in the child's life. Also, this patient had no history of atopy, making atopic dermatitis an unlikely although not impossible diagnosis. Finally, the eczematoid scale seen with atopic dermatitis is typically much less thick and adherent than the scale of psoriasis and doesn't have that condition's typical salmon pink base.

Seborrheic dermatitis is an incorrect choice because, like atopic dermatitis, seborrheic dermatitis is unlikely to be confined to the external auditory meatus. Instead, it is far more likely to be seen behind the ears, on the face, and in the scalp. Moreover, seborrheic dermatitis never manifests itself with nail pitting.

Knowing that psoriasis can affect a single area and knowing how very common it is helped the clinician to reach the correct diagnosis in this case. Considering psoriasis in the differential is the first step, but then that guess must be corroborated by finding other areas of involvement and by asking about family history. A punch biopsy may be performed if necessary.

This patient was treated successfully with triamcinolone 0.1% ointment twice daily, applied sparingly. While a cure is not likely, control is quite possible.