Table of Content


Spring 2015, Vol. 23 No. 1

Hong Kong J. Dermatol. Venereol. (2015) 23, 47

Answers to Dermato-venereological Quiz

Dermato-venereological Quiz

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  1. The clinical differential diagnoses include acanthosis nigricans, tinea versicolor, confluent and reticulate papillomatosis, terra firma-forme dermatosis (dirty neck dermatoses),atopic dermatitis with dirty neck and macular amyloidosis.
  2. Skin scrapings may occasionally reveal Malassezia hyphae or spores. Wood's lamp examination may show yellow fluorescence if Malassezia spp. are present. However, the role of Malassezia spp. is unknown. These may cause an abnormal host response leading to the development of lesions. Histopathology will show varying degree of compact hyperkeratosis, acanthosis, papillomatosis with increased melanin deposition and mild superficial perivascular lymphocytic infiltrate.
  3. The diagnosis is confluent and reticulate papillomatosis of Gougerot and Carteaud (CRP). The diagnosis is arrived on clinical grounds and the excellent response to treatment with minocycline. The patient was treated with six weeks of oral minocycline, resulting in complete clearance of the lesions (Figures 3 and 4). CRP is a rare dermatosis of unknown aetiology that usually appears in teenagers. It is characterised by pigmented reticulated plaques and papular eruptions that usually present over the interscapular area, infra- or inter-mammary area, abdomen and neck area. Rarely, it has been reported to occur on the face and familial cases have been reported. It has been suggested that CRP is a disorder of abnormal keratinisation. The successful response to treatment with antibiotics had led to the theory of bacterial aetiology. An abnormal host response to secondary colonisation by Malassezia or more recently Actinomyces was proposed. CRP is differentiated from other differential diagnoses by the typical clinical appearance of lesions, involvement of the upper trunk and neck, negative fungal staining in scales, unresponsiveness to antifungal treatment and excellent response to minocycline.1

  4. Figure 3

    Figure 4

  5. An excellent response to oral minocycline has been consistently reported.1 Other oral antibiotics such as erythromycin, azithromycin and clarithromycin had been reported effective. Low dose isotretinoin and topical retinoids have been reported to be useful. Other options such as keratolytics, topical antibiotics, topical tacrolimus and calcipotriene have also been used.


1. 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;154:287-93.