Melanuria in a patient with BRAF-mutant metastatic melanoma of unknown primary: Insights on the pathophysiology, differential diagnosis, prognosis, and treatment.

Melanuria is the dark brown discoloration of the urine and an uncommon manifestation in patients with melanoma. It is an ominous sign, usually indicating widespread disease. In this article, through an illustrative case, we discuss the pathophysiological, clinical, and prognostic characteristics of melanuria in melanoma. Moreover, we aim to provide the available data for the prompt diagnosis and treatment of patients presenting with melanuria. We present the case of a 47-year-old man presenting with melanuria and diffure melanosis cutis, who was eventually diagnosed with a BRAF-mutated metastatic melanoma of unknown primary. The patient was started on a BRAF and MEK inhibitor, but he had a rapid disease progression and succumbed to the disease. There is only a limited number of case reports of melanoma patients with melanuria receiving targeted therapies or immune checkpoint inhibitors. In these reports, variable treatment responses have been described. In view of the increasing significance of targeted therapies and immunotherapy for melanoma, more cases are needed to improve our understanding on the prognostic significance of melanuria in the era of novel therapies for melanoma.