A 16-year-old girl presents for evaluation of an asymptomatic brown rash over her central chest and back that developed over the preceding 6 months. She is embarrassed by the appearance.
Confluent and reticulated papillomatosis (CARP), also known as Gougerot-Carteaud syndrome, is an uncommon papulosquamous eruption of unknown etiology. It has been hypothesized that CARP may result from a disorder of keratinization,1 an endocrine imbalance,2 or an abnormal immune response to bacteria or fungi.3,4
Usually, CARP affects adolescents and young adults.5 It is more common in females. It is typically sporadic, although familial cases have been reported.6
Typically CARP presents as hyperpigmented brown-to-gray hyperkeratotic papules that enlarge and coalesce to form plaques that are confluent centrally and reticulated peripherally. There may be overlying scale, and the eruption may have a velvety appearance.
Whereas CARP usually involves the central chest and upper back, it may also affect the neck, upper arms, and axillae. It is generally asymptomatic, although it may be mildly pruritic. It may be associated with acanthosis nigricans (AN) and shares histologic features with AN. However, treatment and resolution of CARP does not affect the course of AN.
Confluent and reticulated papillomatosis is diagnosed clinically. Proposed diagnostic criteria include: 1) presence of scaling brown macules and patches, at least part of which have a reticulated and papillomatous appearance; 2) involvement of the upper trunk and neck; 3) negative fungal staining of scales; 4) no response to antifungal treatment; and 5) excellent response to minocycline.5
Suggested modifications to these diagnostic criteria include the addition of flexural areas to the list of sites of involvement, and response to antibiotics in general, rather than minocycline specifically.7
The differential diagnosis includes tinea versicolor, AN, Darier disease, and Dowling-Degos syndrome. In contrast to tinea versicolor, potassium hydroxide fungal staining is usually negative in CARP. Acanthosis nigricans typically presents with thicker, more velvety plaques lacking reticulation in intertriginous areas. Darier disease often involves the seborrheic areas of the face as well as the nails, which are usually not affected in CARP. Patients with Dowling-Degos syndrome often have pigmented comedones and pitted acneiform scars on the chin.
The treatment of choice for CARP is 2 months of therapy with minocycline or doxycycline, which are effective in most patients.5 Other agents that have been reported to have variable efficacy include other topical and systemic antibiotics,8,9 antifungals directed against Malassezia,10 topical and systemic retinoids,11,12 and 70% alcohol swabbing.13
Without treatment, most patients will improve spontaneously over months to years. Treatment is primarily for cosmetic purposes. The condition often has a chronic course marked by exacerbations and remissions, and may recur after stopping treatment.5,14
The patient was treated with 100 mg minocycline twice daily for 8 weeks, which led to resolution of the eruption on her chest and back. She remains free of recurrence.
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