Diffuse melanosis cutis: a rare manifestation of metastatic melanoma.

Diffuse melanosis cutis (DMC) is an extremely rare and late complication of metastatic melanoma (MM). It involves the progressive blue-grey discolouration of the skin and mucous membranes, occurring approximately 1 year after diagnosis of MM. The pathogenesis of DMC is unknown, although specific growth factors, such as alpha-melanocyte stimulating hormone, hepatocyte growth factor and endothelin-1, released by cancer cells, along with release of melanin precursors in the bloodstream and dermal MM micrometastases producing melanin have been attributed. Even with appropriate therapy, DMC seems to be a poor prognostic factor, with a mean survival time of 4-5 months. Here, we report a case of BRAF-mutated MM who presented with DMC. The patient underwent BRAF/MEK inhibition followed by anti-PDL1 therapy, yet passed away approximately 1 year after diagnosis.