Pediatric Dermatology Consult

Confluent and reticulated papillomatosis

A 17-year-old male presents to the dermatology clinic for brown lesions on his central chest and back that have been present for about a year. The brown areas gradually have become scaly over time. They are asymptomatic. His pediatrician had given him hydrocortisone ointment to apply to the lesions, but there was no improvement. Review of systems was otherwise negative.

Dr. Lawrence F. Eichenfield
On examination, the patient is overweight. Hyperpigmented papules and plaques with mild scale are present on his central chest and back, converging toward the center of the chest and back and extending through the inframammary areas bilaterally. The papules and macules on the periphery of the involved skin create a net-like shape. The remainder of the physical examination is normal.

What’s your diagnosis?

Acanthosis nigricans

Epidermodysplasia verruciformis

Acne vulgaris

Tinea versicolor

Confluent and reticulated papillomatosis

Darier’s disease

Confluent and reticulated papillomatosis of Gougerot and Carteaud, also known as Gougerot-Carteaud syndrome, is an uncommon skin disorder of young individuals characterized by hyperkeratotic or verrucous brown papules or plaques that coalesce centrally and by a reticulated pattern peripherally. It was first described by two French dermatologists, Gougerot and Carteaud, in 1927.1 Initially, the distinct entity of CARP was contested, with some dermatologists believing it to be a variant of acanthosis nigricans. However, CARP is now recognized as a distinct, though rare, dermatosis.

Confluent and reticulated papillomatosis (CARP) Dr. Lawrence F. Eichenfield
CARP commonly affects teens and young adults, with a mean age of onset of 15 years and without gender predilection.2The most common skin findings of CARP are somewhat verrucous or slightly hyperkeratotic brown papules a few millimeters in diameter. They are closely set together to form plaques in the center of the involved area, while those on the periphery of the involved area form a characteristic reticulated pattern. Papules are often scaly, although verrucous papules, especially those found in intertriginous areas, may develop a velvety appearance. Macules and patches may be present as well. The most common areas of involvement include the central chest and back with lesions extending in a rhomboidal fashion superoinferiorly, as well as the neck and axillae.1 Uncommonly, pubic and facial skin may be affected.2 Skin lesions are frequently hyperpigmented; however, cases of hypopigmented variants have been reported in darker-skinned individuals, although these cases have often been misdiagnosed as tinea versicolor.3 The majority of patients are asymptomatic, although some report mild pruritus. Care often is sought for cosmetic concerns.

Histopathology reveals findings similar to those that may be found in acanthosis nigricans and epidermal nevi. Classic characteristics of CARP include hyperkeratosis, papillomatosis, increased basal melanin pigmentation, and mild acanthosis. Occasionally, there may be perivascular lymphocytic infiltrates in the superficial dermis.3,4

The etiology of CARP is unknown. CARP’s resolution in response to antibiotics and the isolation of two bacterial actinomycetes, Rhodococcus and Dietzia papillomatosis, from skin scrapings of CARP patients have led some to believe that its etiology is bacterial. However, no bacterial species have been consistently isolated from CARP patients. The prevailing theory of the past was that CARP was an abnormal host response to the fungus Malassezia furfur. Inconsistent detection of the fungus in skin scrapings, as well as persistence of the skin lesions after fungal clearance with antifungal therapy, has debunked this theory. An underlying disorder of keratinization resulting in hyperproliferation also has been suggested given reports of familial CARP and electron microscopy studies demonstrating focal-enhanced expression of keratin-16 in the stratum granulosom.5 Other theories include a cutaneous response to underlying endocrinopathies, ultraviolet light, and localized amyloidosis.1

Diagnosis and differential

CARP is poorly recognized by clinicians and frequently initially misdiagnosed due to its similar appearance to other disorders, most commonly tinea versicolor and acanthosis nigricans. Davis et al. proposed criteria for diagnosis of CARP requiring 1) presence of scaly, reticulated and papillomatous brown macules and patches; 2) distribution over the upper trunk and neck; 3) negative fungal staining of scales; 4) no improvement following antifungal treatment; and 5) improvement following minocycline.2

Tinea versicolor may appear similar to CARP, but unlike CARP, will respond to antifungal treatment and may demonstrate hyphae and yeast on KOH preparation. Acanthosis nigricans and CARP both may present with velvety, hyperpigmented plaques in individuals of obese habitus or with insulin resistance, but peripheral reticulation will be absent in acanthosis nigricans. However, acanthosis nigricans and CARP may coexist, and this coexistence is not uncommonly seen in individuals with obesity and/or insulin resistance. Darier’s disease may look similar to cases of CARP without pigmentary change, but it often will have accompanying nail changes. Macular or lichen amyloidosis may present with pruritic brown macules or papules, but skin biopsy will have positive amyloid staining. The use of 70% alcohol swabbing to diagnose terra firma-forme dermatosis, with lesions disappearing with swabbing, is classic and used to differentiate it from CARP. Other conditions to consider include seborrheic dermatitis, epidermal nevi, verruca plana, epidermodysplasia verruciformis, and acne vulgaris.1,2,4

Treatment

Minocycline is the first-line treatment for CARP: 80% of patients may have complete resolution with minocycline, while the remainder experience at least 50% clearance of skin lesions.2 However, recurrence after stopping minocycline treatment is not uncommon. The mechanism by which minocycline works is unknown. Second-line treatment for those who cannot tolerate minocycline are macrolide antibiotics.6 Other treatment options with reported success include oral isotretinoin and topical retinoids, including tretinoin gel and tazarotene cream.3,7 Appropriate strength topical corticosteroids may be used for pruritus.

Allison Han, a medical student at the University of California, San Diego
Allison Han

Ms. Han is a medical student at the University of California, San Diego. Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children’s Hospital–San Diego, as well as the vice chair of the department of dermatology and a professor of dermatology and pediatrics at UC San Diego. They report having no conflicts of interest or financial disclosures. Email them at pdnews@frontlinemedcom.com.

Dr. Lawrence F. Eichenfield of the University of California, San Diego
Dr. Lawrence F. Eichenfield

References

1. Clin Cosmet Investig Dermatol. 2016 Aug 25;9:217-23.

2. Br J Dermatol. 2006 Feb;154(2):287-93.

3. Arch Dermatol. 2012 Apr;148(4):505-8.

4. J Am Acad Dermatol. 2003 Dec;49(6):1182-4.

5. Arch Dermatol. 2002 Feb;138(2):276-7.

6. J Am Acad Dermatol. 2001;44(4):652-5.

7. Am J Clin Dermatol. 2006;7(5):305-13.

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