Table of Content


Summer 2012, Vol. 20 No. 2

Hong Kong J. Dermatol. Venereol. (2012) 20, 85

Dermato-venereological Quiz

Dermato-venereological Quiz

RCW Su 蘇志慰 and BKC Yau 游高照

A 60-year-old gentleman presented with an erythematous plaque on his left buttock for more than one year. The lesion was non-itchy and non-tender. His past health was good with no history of immunosuppression.

On examination there was a 1.8x1.2 cm solitary brownish plaque on left buttock with surrounding erythema and double-edged scaling (Figure 1). Examination of other areas of skin, including palms, soles, scalp, nails, genitals and oral mucosa were unremarkable. There was no cervical, axillary or groin lymphadenopathy. Skin scraping for fungus was negative. Complete blood picture, liver and renal function were unremarkable. Incisional skin biopsy of left buttock skin lesion including its scaly edge was performed for histopathological examination (Figure 2).

Figure 1 Solitary brownish plaque on left buttock.

Figure 2 Two parakeratotic columns in an area of invaginated epidermis (H&E stain, original magnification x 200).


1) What are the clinical differential diagnoses?

2) What are the histopathological findings?

3) What is the diagnosis?

4) What are the treatment options for this condition?

Answers to Dermato-venereological Quiz

  1. Differential diagnosis includes porokeratosis, Bowen's disease, extra-mammary Paget's disease and mycosis fungoides.
  2. Histopathological examination of skin showed moderate acanthosis. There are two parakeratotic columns with features of cornoid lamella in an area of invaginated epidermis (Figure 2, arrow A). The underlying granular cell layer is diminished (Figure 2, arrow B). The upper reticular dermis shows moderate perivascular lympho-histiocytic infiltrate. No evidence of malignancy is seen.
  3. The histological findings are consistent with porokeratosis. The most frequent presentation of porokeratosis is disseminated superficial porokeratosis, located on extremities in an actinic distribution. Other clinical presentations include plaque type (Mibelli), linear type, punctate porokeratosis of palms and soles, and porokeratosis palmaris, plantaris et disseminata.
  4. Treatment should be individualized based on size, location and number of lesions. General measures include avoidance of excessive sun exposure, emollients and keratolytics for dry skin and hyperkeratotic lesions. Localized lesions may be treated by surgical excision, cryotherapy, laser ablation, topical 5-fluorouracil or imiquimod. Oral retinoids have been reported to improve widespread or refractory lesions, but there is a tendency for recurrence on discontinuation. Malignant degeneration into squamous cell carcinoma has been reported occasionally in lesions of porokeratosis. The risk is higher in older or immunosuppressed patients, long standing lesions and linear porokeratosis. Continued follow up and biopsy of suspicious lesion is indicated.