RECENT-ONSET SKIN CHANGES
A 54-year-old woman with a history of psoriasis presents with a 4-week history of skin lesions (Figure 1) that she initially thought were a psoriasis flare-up. The area is itchy and has not improved despite 4 days of prednisone 20 mg. Her current medications are fexofenadine, levothyroxine, and etanercept. Her skin findings on physical examination are shown in the image here (image courtesy of Dr. Eden Lake). A biopsy is performed, and the pathology report reveals interstitial histiocytes and dermal solar elastosis.
Given the likely diagnosis, which of the following is correct?
A. Topical antifungal is the best treatment.
B. The skin findings are often associated with an underlying trigger.
C. First-line treatment is oral dapsone.
D. The skin findings often self-resolve, so treatment is based on the patient's symptoms.
E. The patient has an increased risk of erythema nodosum.
DISCUSSION
The diagnosis of this patient, based on the clinical findings and histopathology, is granuloma annulare (GA). GA affects both children and adults and tends to affect women more than men. It is relatively common, yet its etiology is unknown. Several theories point to environmental factors and exposures, infections, and genetics as potential associations or causes (Piette & Rosenbach, 2016). On histopathology, interstitial histiocytes and dermal solar elastosis are seen, indicative of GA when considering the clinical presentation as well (Keimig, 2015). There are different clinical variants of this disorder, such as localized, generalized, subcutaneous, perforating, and patch GA. Localized GA is the most common and is this patient's diagnosis given her lesions are localized and erythematous and lack superficial scale, with associated central clearing. Generalized GA is widespread, frequently affecting the trunk and extremities. Subcutaneous GA is most prevalent in children and presents as painless nodules that are found on the extremities or scalp. Perforating GA presents initially as erythematous papules, which eventually become umbilicated papules with exudate. Patch or macular GA lacks scale and commonly affects the proximal extremities, although the involvement may be more generalized (Keimig, 2015).
Regarding this patient's treatment, localized GA is usually self-limited and does not require treatment. However, some patients may desire therapy because of the prolonged time to resolution of the skin lesions, which may be 2 years or more, for mild pruritus or for cosmetic reasons (Piette & Rosenbach, 2016). If treatment is desired, first-line therapy is corticosteroids, either (high-potency) topical or intralesional. Treatment response is variable in patients, and topical corticosteroid application requires 2-4 weeks before determining if there has been a treatment response. Patients taking long-term topical or intralesional corticosteroids may experience side effects such as cutaneous atrophy and hypopigmentation (Wang & Khachemoune, 2018).
Given the above discussion, the correct answer to this case is "D," as GA is self-limited and will typically resolve without treatment. Option A is incorrect as it refers to the treatment of tinea corporis, which would not have these histopathologic findings, and the skin findings would appear scaly upon physical inspection. As tinea corporis would be considered in the differential diagnosis for this case, it could be easily distinguished by performing a KOH preparation (Ely, Rosenfeld, & Seabury Stone, 2014). Choice B is incorrect as GA has an unknown cause, although various etiologies have been proposed. This answer choice refers to annular lesions such as in erythema annulare centrifugum, another diagnosis to consider in the differential for GA. In the pathology report for erythema annulare centrifugum, a perivascular lymphocytic infiltrate is characteristic (Kim, Lee, Lee, & Park, 2016). Option C is incorrect, as first-line treatment for localized GA, if deciding to treat, would be high-dose topical corticosteroids or intralesional corticosteroids (Wang & Khachemoune, 2018). Oral dapsone would be the treatment of choice for alternative diagnoses such as erythema elevatum diutinum, a condition that can present clinically similar to GA but differs in its histopathology, as a neutrophilic infiltrate would be observed (Mancano, Dinato, Almeida, & Romiti, 2018). Finally, Choice E is incorrect as GA is not associated with erythema nodosum. Choice E may be correct for a diagnosis of cutaneous sarcoidosis, which is associated with a higher likelihood of erythema nodosum. Cutaneous sarcoidosis may have a similar clinical appearance to GA but would appear as noncaseating granulomas on histopathology (Wanat & Rosenbach, 2015).
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