2019 Volume 68 Issue 2 Pages 388-394
We report a case of melanuria with dark-yellow urine. Dark-yellow urine normally indicates blood in urine, bilirubinuria, or urobilinuria. In this case, because no abnormal values for red blood cells, bilirubin, and urobilinogen were detected by a semiqualitative urine test, we suspected melanuria on the basis of clinical diagnosis. Then, the urine sample was found positive for melanin using the Thormählen test. To confirm melanuria, we quantified melanin marker by high-performance liquid chromatography (HPLC). The result showed that 4 melanin markers, namely, 5-S-CD, PTCA, PDCA, and 4-AHP, were detected by HPLC. Importantly, melanuria did not always appear in the urine. The dark-yellow color changed to yellow or straw-colored a few days after the treatment with the immune checkpoint inhibitor. The intermittent appearance of melanuria may reflect the progression of melanoma or the destruction of melanoma cells by the anti-cancer treatment, especially the immune checkpoint inhibitor. Thus, these results suggest that the detection of melanin in dark-yellow urine by performing the Thormählen test could be useful for determining the progression of melanoma and the response to treatment.
