CARP_0912 Derm Clinic 2
Over the course of several months, an otherwise healthy 17-year-old woman developed an asymptomatic and progressively worsening rash over her torso. Topical emollients and antifungal creams provided no improvement in her condition.
Physical examination revealed hyperpigmented, thin papules with a faintly verrucous surface coalescing into reticulate plaques over the woman’s central and inframammary chest, flanks, and back. KOH preparation of skin scrapings from the involved areas was negative for yeast or fungal forms.
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This patient’s presentation was highly suspicious for confluent and reticulated papillomatosis of Gougerot and Carteaud (CARP). CARP is an uncommon dermatosis of unclear etiology. The initial description of this condition was published in 1927 by the physicians for whom it is named. Since then, others have attempted to further delineate the clinical features and pathogenesis, but the rarity of the condition has limited these studies.1 The first report of clearance with antibiotics was documented in 1965,2 and response to antibiotics is now considered one of the distinguishing features of CARP.
CARP is most common in adolescents and young adults. Women and those with darker skin tend to be more susceptible. However, CARP has been seen in all ages and races.3
CARP classically presents as slowly progressive, asymptomatic, velvety to slightly verrucous, sessile brown papules coalescing into reticulated thin plaques, most commonly on the trunk, neck, and axillae. Many variations in appearance and distribution have been described, but these are encountered much less frequently.3
CARP is most often misdiagnosed as acanthosis nigricans or tinea versicolor. There is a broad differential diagnosis for CARP, but this discussion will focus on these two common dermatoses and how they can be differentiated from CARP. Acanthosis nigricans is a velvety hyperpigmentation of the skin of the neck, axillae, and, less often, trunk. The appearance is not reticulated as in CARP. Acanthosis nigricans is strongly associated with obesity, insulin resistance, and dyslipidemia. There are no well-established systemic assocations in individuals with CARP.
Tinea versicolor is a common eruption of the trunk caused by overgrowth of pityrosporum. Tinea versicolor consists of variably hyper- or hypopigmented macules on the trunk that produce a powdery scale on scraping. If you suspect CARP, it is important to exclude a diagnosis of tinea versicolor. A KOH preparation of involved skin will be negative in cases of CARP and will yield yeast and hyphal forms with the “spaghetti and meatballs” morphology in cases of tinea versicolor. Tinea versicolor can be treated effectively with antifungals, while CARP does not respond to this therapy.
The following diagnostic criteria have been proposed for CARP: (1) scaling brown macules and patches, at least part of which appear reticulated and papillomatous; (2) involvement of the upper trunk and neck; (3) fungal staining of scales is negative; (4) no response to antifungal treatment; and (5) excellent response to minocycline (Dynacin, Minocin, Myrac).1
Although generally unnecessary, skin biopsy is indicated if the presentation is unusual or response to treatment is poor. Biopsy will show papillomatosis, hyperkeratosis, and mild acanthosis of the epidermis, with variable hyperpigmentation of the basilar layer.1,3,4 Acanthosis nigricans has similar histopathologic features, so correlation with clinical findings is important. Special stains for fungus are usually negative.
There are many hypotheses regarding the etiology of CARP. Some propose that this is a disorder of keratinization. In support of this, CARP has been shown to improve with medications (i.e., retinoids, vitamin D analogues) that act to normalize keratinization.3 Others believe Pityrosporum species to be causative, but proving this is difficult, as pityrosporum are part of the normal skin flora.
In addition, tinea versicolor is characterized by an excess of pityrosporum and is a clinical mimicker of CARP, so it has been argued that this association may have been the result of misdiagnosis.3 CARP has also been linked to endocrinopathies, UV light exposure, and even genetic inheritance.3 However, none of these proposed mechanisms explain the response to antibiotics.
More recently, a newly described actinomycete was cultured from skin scrapings of an individual with CARP, and this bacterium was shown to be suspectible to antibiotics commonly used to treat CARP. However, it is difficult to prove causality, as it remains unclear whether this organism is simply a contaminant, commensal, or truly pathogenic.2 Additionally, antibiotics may be exerting an anti-inflammatory rather than an antibacterial effect, which is why more studies are needed to determine exactly how and why they work in this condition.
The treatment of choice for CARP is minocycline 100 mg orally b.i.d. for at least four weeks. Several other antibiotics have shown efficacy including doxycycline, clarithromycin (Biaxin), fusidic acid, erythromycin, and azithromycin (Zithromax, Zmax)—all requiring a several-week course of therapy for improvement/clearance.5
Other treatments that are reported to be beneficial are topical retinoids, oral retinoids, topical vitamin D analogues, and even swabbing with 70% alcohol.3,6 There is the possibility of a slight risk of recurrence after treatment; if this occurs, a repeat course of antibiotics is usually effective.
The patient in this case received a two-month course of minocycline with near complete resolution of the rash.
Erin L. Reese, MD, is assistant professor in the Department of Dermatology at Virginia Commonwealth University in Richmond.
- Davis MD, Weenig RH, Camilleri MJ. Confluent and reticulate papillomatosis (Gougerot-Carteaud syndrome): a minocycline-responsive dermatosis without evidence for yeast in pathogenesis. A study of 39 patients and a proposal of diagnostic criteria. Br J Dermatol. 2006;154:287-293.
- Natarajan S, Milne D, Jones AL, et al. Dietzia strain X: a newly described Actinomycete isolated from confluent and reticulated papillomatosis. Br J Dermatol. 2005;153:825-827.
- Scheinfeld N. Confluent and reticulated papillomatosis : a review of the literature. Am J Clin Dermatol. 2006;7:305-313.
- Tamraz H, Raffoul M, Kurban M, et al. Confluent and reticulated papillomatosis: clinical and histopathological study of 10 cases from Lebanon. J Eur Acad Dermatol Venereol. 2011. [Epub ahead of print].
- Jang HS, Oh CK, Cha JH, et al. Six cases of confluent and reticulated papillomatosis alleviated by various antibiotics. J Am Acad Dermatol. 2001;44:652-655.
- Berk DR. Confluent and reticulated papillomatosis response to 70% alcohol swabbing. Arch Dermatol. 2011;147:247-248.