Ali Alaa A, Saleem Zana Sidiq M, Jabali Shakir S, Ibrahim Nashwan M R, Hughson Michael D
University of Sulaimani College of Medicine, Shorsh Teaching and Hiwa Oncology Hospitals, Sulaimani, Iraq.
University of Duhok College of Medicine, Duhok, Iraq.
BMC Nephrol. 2025 Jul 11;26(1):375. doi: 10.1186/s12882-025-04319-5.
Melanin deposition in the kidney is rare and appears limited to the conditions of oculocutaneous albinism and malignant melanoma with melanuria. Melanin is generally an insoluble polymer, and it is curious how people with albinism who have little or no skin pigmentation can secrete melanin into the bloodstream, have it pass through the glomerular filtration barrier, and be absorbed by renal tubules.
The concentration and solubility of melanin were analyzed in kidney tissue and urine of a renal transplant donor who had a pre-nephrectomy biopsy performed on a black kidney. Genetic testing of a donor blood sample found a novel homozygous Hermansky-Pudlak syndrome (HPS) HPS1 mutation (c.70G > T; p.Glu24Ter). Melanin was extracted from a 24-hour urine collection, and tissue and urine melanin concentrations were determined by spectrophotometry.
In the kidney, non-melanosomal melanin was deposited as granules in the proximal tubular epithelium and as large aggregates within macrophages in renal tubular lumens. The kidney melanin concentration was 2 mg/g of tissue. Urine melanin was mainly water-soluble, with an excretion of eumelanin that is within a reported normal range.
Water-soluble melanin was excreted in the urine of a kidney donor with a novel HSP1 mutation predicted to produce a truncated protein. This resulted in melanin pigmentation of a kidney transplanted into a normally pigmented sibling. Donor and recipient are healthy 3 years after the transplant. Nevertheless, HSP can be associated with kidney, colon, and lung pathology, and the long-term outlook for the recipient kidney and donor's health is uncertain.
黑色素在肾脏中的沉积较为罕见，似乎仅限于眼皮肤白化病和伴有黑尿症的恶性黑色素瘤的情况。黑色素通常是一种不溶性聚合物，令人好奇的是，几乎没有或没有皮肤色素沉着的白化病患者如何能将黑色素分泌到血液中，使其通过肾小球滤过屏障，并被肾小管吸收。
对一名肾移植供体进行分析，该供体在肾切除术前对其黑色肾脏进行了活检，分析了肾脏组织和尿液中黑色素的浓度和溶解度。对供体血样进行基因检测，发现了一种新的纯合Hermansky-Pudlak综合征（HPS）HPS1突变（c.70G＞T；p.Glu24Ter）。从24小时尿液收集样本中提取黑色素，通过分光光度法测定组织和尿液中的黑色素浓度。
在肾脏中，非黑素小体黑色素以颗粒形式沉积在近端肾小管上皮中，并以大聚集体形式存在于肾小管腔中的巨噬细胞内。肾脏黑色素浓度为2mg/g组织。尿液中的黑色素主要是水溶性的，真黑素排泄量在报告的正常范围内。
一名具有预测会产生截短蛋白的新型HSP1突变的肾供体尿液中排泄出了水溶性黑色素。这导致移植到正常色素沉着的同胞体内的肾脏出现黑色素沉着。移植后3年，供体和受体均健康。然而，HSP可能与肾脏、结肠和肺部病变有关，受体肾脏和供体健康的长期前景尚不确定。
