A case of Diffuse Melanosis and Melanuria

Dr Simonetta Piana, at Azienda Unità Sanitaria Locale di Reggio Emilia–IRCCS, Reggio Emilia, Italy and colleagues has reported a rare case of Diffuse Melanosis and Melanuria. The case has appeared in the NEJM.

The advanced stages of melanoma malignum (MM) can manifest with metastases into the lymph nodes, liver, lung, brain, bones, and skin. The skin and subcutaneous tissue metastases are relatively rare. Diffuse melanosis with melanuria is a rare complication of metastatic malignant melanoma that is associated with a very poor prognosis. Diffuse melanosis cutis (DMC) is a very rare sign of malignant melanoma progression. The condition usually develops after approximately one year from melanoma diagnosis in a patient with metastatic tumours and after anticancer treatment with cytostatic medications. Until 2015, 70 cases of DMC were reported, however, the pathophysiological mechanisms of the condition have not been elucidated

As the history goes, a 47-year-old woman presented to the dermatology clinic with diffuse, progressive discolouration of the skin, nails, and oral mucosa and darkening of the urine that had developed over a period of 4 weeks. Eight years before presentation, she had received a diagnosis of melanoma after undergoing biopsy of a lesion on the right shoulder.

At that time, the melanoma was treated with wide surgical excision; sentinel lymph node biopsy was negative. Six months before presentation, the patient had received a diagnosis of metastatic melanoma, with metastases found in the brain, lung, liver, and vertebrae. Because the melanoma was BRAF V600E positive, the patient was treated with dabrafenib and trametinib as well as with radiation therapy to the vertebral lesions.

The exact mechanism of Diffuse melanosis and melanuria is unknown, but it is thought to involve cytolysis of melanoma cells, leading to the release of large amounts of melanin and melanin precursors into the circulation. Despite treatment, the disease progressed, and the patient died 2 weeks after presentation.