Pictorial Case Study: dermatosis papulosa nigra

The case: This 48-year-old patient had been aware of a number of small, brown papules on the upper part of her chest ever since her teenage years. They had gradually spread and increased in number. The lesions were completely symptomless, but recently so many friends had remarked on the 'rash' that she felt embarrassed to wear low-cut shirts, dresses or swimwear.

The patient had a number of small, brown papules on her chest
The patient had a number of small, brown papules on her chest

Diagnosis and management
A diagnosis of dermatosis papulosa nigra was made and she was reassured that the condition had no sinister implications, but that she could expect more lesions to appear. Treatment would only need to be considered for cosmetic reasons.

Dermatosis papulosa nigra is a benign condition that occurs most commonly in those with black skin. The cause is unknown but occasionally there is a family history of the condition raising the possibility of a genetic factor.

It is more common in women, tends to develop in the teenage years and the number of lesions tends to increase with age. On examination, numerous symptomless small, pigmented and sometimes pedunculated papules are seen. They most frequently appear on the cheeks and the forehead but they also occur on the neck, upper back and chest. Histological examination following biopsy of a lesion will be similar to that of seborrhoeic keratosis. Treatment is unnecessary as there is no risk to health. Some patients, however, may be distressed by the appearance of the lesions and curettage, cryotherapy or laser treatment can be offered if requested for cosmetic reasons.

Possible differential diagnosis

  • Melanocytic naevi.
  • Seborrhoeic keratosis.

Differential diagnosis
Seborrhoeic keratosis (basal cell papilloma)

  • Common benign tumour that develops in older age groups.
  • Cause unknown; thought to be degenerative in nature; sometimes follows sunburn or irritating skin problem.
  • Develops as a proliferation of epidermal cells.
  • Sudden multiple eruption of lesions may be associated with some underlying malignancy.
  • Can occur anywhere on the body other than the soles, palms or mucous membranes.
  • Single or multiple slightly raised, skin-coloured, brown or black lesions, with warty appearance that appear 'stuck' on to the skin.
  • May resemble malignant melanoma - dermoscopy and/or biopsy may be required to confirm diagnosis.
  • Treatment unnecessary unless causing discomfort, rubbing on clothes or unsightly.
  • Sometimes become inflamed and crusted.
  • Treatment includes cryotherapy, curettage and cautery, laser treatment or shave biopsy.
  • Dr Jean Watkins is a retired GP in Hampshire.

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