Dermatoscopy of confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome).

Also referred to as Gougerot-Carteaud syndrome, confluent and reticulated papillomatosis (CARP) is an acquired keratinization disorder of uncertain etiology. Clinically, it is typically characterized by symptomless, grayish-brown, scaly, flat papules that coalesce into larger patches with a reticular pattern at the edges. Sites most commonly affected include the anterior and/or posterior upper trunk region [1–3]. Although its clinical diagnosis is usually straightforward, the distinction from similar pigmentary dermatoses may sometimes be challenging, especially in case of lesions occurring in atypical locations [1–3]. In recent years, dermatoscopy has been shown to be useful in the clinical diagnosis of several “general” skin disorders, thus reducing the number of cases requiring biopsy [4–8]. The objective of the present study was to describe the dermatoscopic features of CARP in order to facilitate its noninvasive diagnosis. Eight individuals (3 women/5 men; mean age 29.2 years, range 18–51 years; mean disease duration 3 months, range 1–9 months) with CARP (diagnosed on the basis of histological findings and clinical criteria)  were included in the study. None of the patients had been using systemic or topical therapies for at least six weeks. In each patient, a handheld noncontact polarized dermatoscope (DermLite DL3 × 10; 3 Gen, San Juan Capistrano, CA, USA) equipped with a camera (Coolpix® 4500 Nikon Corporation, Melville, NY, USA) was used to take a dermatoscopic picture of a single target lesion (flat desquamative papule). All pictures were evaluated for the presence of specific morphological patterns by two of the authors (EE, GS). In all cases (100.0 %), we observed the same findings: fine whitish scaling as well as homogeneous, brownish, more or less defined, flat polygonal globules separated by whitish/ pale striae, thus creating a cobblestone pattern (Figure 1a, b). The shade of the flat globules was dark-brown (Figure 1a) in five (62.5 %) and light-brown (Figure 1b) in three (37.5 %) cases. To the best of our knowledge, there has only been one previous publication on dermatoscopy of CARP. In that particular study, findings included superficial white scales (likely due to parakeratosis and compact hyperkeratosis), brownish pigmentation with poorly defined borders (thought to correspond to hyperpigmentation of the basal layer), and a pattern of “sulci and gyri” (depressions and elevations, presumably as a result of papillomatosis) . In the present study, we were able to confirm some of the aforementioned findings (white scaling and brownish pigmentation), however, the brownish areas in our patients consistently showed a cobblestone pattern (closely aggregated, squarish/polygonal, flat globules). This peculiar aspect could be due to the combination of basal hyperpigmentation, acanthosis, and papillomatosis, with relative sparing of the normal network of furrows of the skin surface. Accordingly, one might speculate that the different pattern of pigmentation found in the previous study might have resulted from the disruption of these physiological grooves due to more pronounced/irregular acanthosis/ papillomatosis. Remarkably, the detection of fine whitish scaling and brownish areas in a cobblestone or “sulci and gyri” pattern might be useful in distinguishing CARP from its differential diagnoses  (Table 1). These primarily include 1) tinea (pityriasis) versicolor, which is characterized by a pigmented network composed of brownish stripes and fine scales [11],