CARP_0412 Derm Dx
A 16-year-old black female presents complaining of an eruption between her shoulder blades. She is not sure when the eruption first appeared, but her mother complains that it is unsightly.
The patient denies pain or itch in the affected area. She also denies any prior past medical history or medication use. She reports that her sister has psoriasis and her brother has atopic dermatitis. On exam, she is an obese but otherwise well-appearing black female with normal vital signs. Physical exam is significant only for the eruption pictured below.
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Confluent and reticulated papillomatosis (CARP) is a rare disorder that typically begins in puberty. Women are affected approximately 2.5 times more often than men, and blacks are twice as likely to be affected than whites.
Initially CARP presents as small papules, usually appearing in the intermammary, epigastric or interscapular region. The lesions enlarge and become hyperpigmented. Centrally, they coalesce and become confluent. At the periphery, they have a reticulated morphology. Lesions are usually asymptomatic, but patients rarely complain of itch.
The etiology of CARP is unknown. Some believe that CARP is caused by endocrine abnormalities, as there have been reports of an association with obesity (which is the situation in this case), irregular menstruation, diabetes, pituitary disorders and thyroid disease. However, the majority of patients are healthy with no such underlying comorbidities.1, 2
The diagnosis is clinical and based on the characteristic appearance of centrally confluent and peripherally reticulated hyperpigmented papules and plaques in the typical distribution described above.
Tinea versicolor may present in a similar distribution, but lesions are hyper or hypopigmented macules and patches with slight scale, and do not have a papillated appearance as in CARP. Histologically CARP resembles acanthosis nigricans and is characterized by hyperkeratosis and papillomatosis. 1, 2
Treatment and prognosis
Patients are often unsatisfied with CARP treatment, as the disorder may not respond to therapy or may relapse when therapy is completed. The most commonly described therapy is minocycline, 100 mg twice a day for six weeks. Other treatment modalities reported include various other oral antibiotics, oral retinoids and topical lactic acid and urea creams. In this case, the patient completed a six week course of minocycline, but did not improve.
Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.
1. Bolognia J, Jorizzo JL, Rapini RP. “Chapter 109: Benign Epidermal Tumors and Proliferations.” Dermatology. St. Louis, Mo.: Mosby/Elsevier, 2008.
2. James WD, Berger TG, Elston DM, and Odom RB. “Chapter 11: Pityriasis Rosea, Pityriasis Rubra Pilaris, and Other Papulosquamous and Hyperkeratotic Diseases.” Andrews’ Diseases of the Skin: Clinical Dermatology. Philadelphia: Saunders Elsevier, 2006.