DISCUSSION
This case demonstrates a common quandary in dealing with skin disease in which so much emphasis is placed on treatment that the acquisition of a correct diagnosis is overlooked. Short therapeutic/diagnostic trials are quite reasonable at the outset, but when these fail, the definitive procedure is often a biopsy.
In this case, both application of cantharidin and a trial of cimetidine are based on the assumption that the lesion is a wart, an unlikely diagnosis because of previous failure of wart therapies. Treatment with a urea-based lotion would likely soften the lesion and perhaps make it less prominent, but this approach is not driven by an actual diagnosis.
Punch biopsy, which is the next logical step in addressing this lesion, showed hyperkeratosis, acanthosis, focal spongiosis, and focal parakeratosis in the epidermis. Equally important, the biopsy failed to show any signs of human papillomavirus-related tissue changes or other infectious processes. Taken in context with the history, the findings were interpreted as consistent with a form of lichen simplex chronicus, which is also known as neurodermatitis. When the affected area becomes this sharply demarcated and lesional, the term neurodermatitis circumscripta is often used. Scratching, rubbing, or
picking become habitual, even gratifyingly pleasant.
The biopsy could have revealed a number of findings, including signs of deep fungal or atypical mycobacterial infection, even neoplasia, so microscopic examination was definitely worthwhile. The radiograph obtained several years previously served to rule out underlying bony disease.
Treatment was bedtime application of topical clobetasol cream under occlusion. Covering the treated lesion provided a barrier to the patient's fingernails and potentiated the class 1 corticosteroid, which resulted in resolution of the lesion over a 2-month period. Other treatments include intralesional injection of triamcinolone 10 mg/cc.
This patient's loss of pigment was permanent and thought to have been caused by previous liquid nitrogen treatments. The chances that the lesion will reform are quite high given the habitual nature of the problem. JAAPA
Joe Monroe practices at the Dawkins Dermatology Clinic, Oklahoma City, and is the department editor for Dermatology Digest. The author has indicated no relationships to disclose relating to the content of this article.