Confluent and reticulated papillomatosis (CARP) is a relatively rare form of dermatosis that occurs in both sexes and all ethnic groups.1 However, 2 recent studies suggest that CARP occurs more commonly in white patients and ethnicities with lighter skin.1,2 In addition, the average age of onset and sex of CARP patients varies by ethnicity. Although CARP can occur in patients ranging in age from 5 to 63 years, the average age of onset is 15 years in predominantly white populations and 29 years in Southeast Asian populations.2,3 The condition presents more often in white women than white men but more often in Asian men than Asian women.1,3
Many theories have been proposed to explain the etiology and pathogenesis of CARP. The condition originally was thought to be caused exclusively by the fungal organism Malassezia furfur. However, not all cases of CARP respond to antifungal medications, and the organism may not be identified on microscopic examination.4 For these reasons, alternative etiologies for this condition, including bacterial infection, have been suggested.1
In one study, Natarajan et al isolated Dietzia, a bacterial genus that is susceptible to minocycline, which is commonly used in the treatment of CARP.5 However, another study reported that not one consistent organism has been identified from skin scrapings.6 The efficacy of antibacterial therapies may be due to their anti-inflammatory properties.4,6
Another potential causal mechanism is an acquired or genetic pathologic process of keratinization, which can be seen on histologic examination.1 However, this model does not account for cases of CARP that resolve with antibacterial therapy alone, even when no bacterial organisms were seen on microscopic examination.
A correlation exists between CARP and medical conditions such as obesity and diabetes mellitus.1,6 Increased body habitus has been identified as an independent risk factor for the development of CARP, and subsequent insulin resistance has been theorized to trigger epidermal proliferation. Increased circulating insulin may bind to epidermal and fibroblast growth factors, contributing to reduced apoptosis of epidermal cells.6 Therefore, obesity and diabetes may be risk factors for CARP. Thus, CARP may not be attributable to one causative factor but may result from a variable interplay of the aforementioned factors.7
CARP is largely asymptomatic and limited to the skin, with no systemic involvement.6 The lesions are found mostly on the upper trunk and axillae and very rarely on the lower limbs. In women, the patches can appear in the axillae or submammary creases with a velvety texture.6 Clinical diagnosis of CARP is made largely by physical examination, with confirmation by histologic examination.
The general morphologic characteristics of CARP involve hyperkeratotic brown scaly patches with reticulation and papillomatosis in at least a portion of the lesions.2 On dermoscopy, CARP classically displays increased melanin pigmentation and basket-weave hyperkeratosis that invaginates into the epidermis. A white scale may overlay brown pigmentation, and this may be a unique finding of CARP that can eliminate other similar conditions from the differential diagnosis.6 The patches may display rippling or reticulation in a “sulci and gyri” pattern.7 Cobblestone patterns due to basal hyperpigmentation and papillomatosis also are possible.8
Acanthosis nigricans has a similar appearance on physical examination and is closely associated with CARP. Notably, a unique feature of CARP is the presence of beading elastic fibers around mildly dilated vasculature. These findings are not present in acanthosis nigricans, and, thus, this histologic feature often is used to differentiate the 2 conditions.1 The presence of follicular plugging and anastomosis of rete ridges in CARP also may help to differentiate CARP from acanthosis nigricans.9
Other conditions with similar appearance include tinea (pityriasis) versicolor, amyloidosis cutis dyschromica, lichen planus pigmentosus, Dowling-Degos disease, terra firma-forme dermatosis, and prurigo pigmentosa.3,10 A diagnosis of tinea versicolor is dependent on microscopic findings of hyphae of M furfur, which are not consistently present in CARP.9 Although CARP may appear with similar coloration to amyloidosis cutis dyschromica, the reticulation found in CARP is distinct from the rippling pattern seen in amyloidosis. In addition, CARP does not display amyloid deposits on histopathology.6 Lichen planus pigmentosus may appear similar grossly but displays coarse gray-blue and brown globules when examined by dermoscopy.8 Dowling-Degos disease notably lacks papillomatosis and tends to affect intertriginous areas.10 Terra firma-forme dermatosis presents with verrucous plaques and retention hyperkeratosis; the latter can be lightened with alcohol, which is not a characteristic of CARP.4 If a patient presents with complaint of pruritus, a diagnosis of prurigo pigmentosa may be more likely and can be confirmed by histologic examination for lymphocytic infiltrate.1
Numerous treatment options are suggested for management of CARP. Antibiotics (especially minocycline and azithromycin) and antifungals are used most commonly2;they are associated with variable success and high rates of recurrence.Carrozzo et al reported calcipotriol ointment to be an effective topical treatment that may reduce risk of recurrence.10 CARP has been successfully treated with retinoids and vitamin D, which often are used in disorders of keratinization.1 Bernardes Filho et al suggest that weight loss may contribute to greater therapeutic success and minimize the recurrence of the condition.7
The patient in this case was prescribed a 6-week trial of minocycline, and the lesion regressed.
Joanne Jacob, BS, and Emily Burns, BA, are medical student at Baylor College of Medicine, and Christopher Rizk, MD, is a dermatologist at Elite Dermatology in Houston, Texas.
1. Scheinfeld N. Confluent and reticulated papillomatosis. Am J Clin Dermatol. 2006;7(5):305-313.
2. 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(2):287-293.
3. Huang W, Ong G, Chong WS. Clinicopathological and diagnostic characterization of confluent and reticulate papillomatosis of Gougerot and Carteaud: a retrospective study in a South-East Asian population. Am J Clin Dermatol. 2015;16(2):131-136.
4. Pascoe D, Morrell DS. Progressive truncal “dirty skin”: confluent and reticulated papillomatosis. Pediatr Ann. 2007;36(12):810-813.
5. Natarajan S, Milne D, Jones AL, Goodfellow M, Perry J, Koerner RJ. Dietzia strain X: a newly described actinomycete isolated from confluent and reticulated papillomatosis. Br J Dermatol. 2005;153(4):825-827.
6. Lim JH, Tey HL, Chong WS. Confluent and reticulated papillomatosis: diagnostic and treatment challenges. Clin Cosmet Investig Dermatol. 2016;9:217-223.
7. Bernardes Filho F, Quaresma MV, Rezende FC, Kac BK, Nery JA, Azulay-Abulafia L. Confluent and reticulate papillomatosis of Gougerot-Carteaud and obesity: dermoscopic findings. An Bras Dermatol. 2014;89(3):507-509.
8. Errichetti E, Maione V, Stinco G. Dermatoscopy of confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome). J Dtsch Dermatol Ges. 2017;15(8):836-838.
9. Tamraz H, Raffoul M, Kurban M, Kibbi AG, Abbas O. Confluent and reticulated papillomatosis: clinical and histopathological study of 10 cases from Lebanon. J Eur Acad Dermatol Venereol. 2013;27(1):e119-e123.
10. Carrozzo AM, Gatti S, Ferranti G, Primavera G, Vidolin AP, Nini G. Calcipotriol treatment of confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome). J Eur Acad Dermatol Venereol. 2000;14(2):131-133.