Confluent and Reticulated Papillomatosis

Confluent and reticulated papillomatosis (CARP) was first described >60 years ago. It is distinct from acanthosis nigricans. This article presents the results of a review of the literature in MEDLINE through May 2006 using the terms ‘confluent and reticulated papillomatosis’, ‘reticulated and confluent papillomatosis of Gougerot and Carteaud’, and ‘reticulated papillomatosis’.

A recent report has linked the presence of Dietzia spp. (family: Dietziaceae; suborder: Corynebacterineae; order: Actinomycetales) in the skin to CARP. CARP has also been linked to defects in keratinization. Other possible causes of CARP that have been suggested but seem less likely include endocrine abnormalities, Pityrosporum, a reaction to UV light, and a variation of cutaneous amyloidosis. CARP has been reported worldwide and occurs in both sexes, all age groups, and all races. The disorder can initially manifest as hyperkeratotic or verrucous papules that coalesce to form a reticular pattern peripherally and confluent plaques centrally.

Although a variety of treatments for CARP exist, oral minocycline 50–100mg twice daily has been the preferred treatment. However, recent reports of the effectiveness of azithromycin 250-500mg three times weekly may make azithromycin the preferred treatment for CARP, since it has a more benign adverse effect profile than minocycline. Other effective antibacterial treatments include fusidic acid 1000mg daily, clarithromycin 500mg daily, erythromycin 1000mg daily, tetracycline 500mg twice daily, and cefdinir 300mg twice daily. If a recent finding that CARP is caused by a bacterial microorganism is replicated, treatment should likely be determined by bacterial sensitivities, antibacterial adverse effect profiles, and cost considerations. Other oral treatments of CARP that are effective but currently disfavored because of the effectiveness of minocycline include isotretinoin, acitretin, and etretinate. There have been mixed reports regarding the effectiveness of topical treatments, which include selenium sulfide, ketoconazole cream, tretinoin, tazarotene, tacalcitol, and calcipotriene (calcipotriol).