Division of Rheumatology and Immunology, Department of Medicine, Duke University, Durham, NC, 27710, USA.
Division of Rheumatology, Department of Medicine, Hospital del Salvador, Santiago, Chile.
Curr Allergy Asthma Rep. 2021 Mar 5;21(3):19. doi: 10.1007/s11882-021-01002-1.
Ochronosis and alkaptonuria are manifestations of the same condition-a rare autosomal recessive disorder resulting from a constitutional lack of homogentisate 1,2-dioxygenase (HGD) with the consequent accumulation of homogentisic acid (HGA). In ochronosis, HGA undergoes autoxidation as well as enzymatic oxidation to form an ochronotic pigment that accumulates in cartilage and connective tissues. In the beginning, there is homogentisic aciduria and pigmentation of cartilages and other connective tissues. In later years, generalized osteoarthritis of the spine and large joints, termed ochronotic arthropathy, develops.
The diagnosis is confirmed by quantitative measurement of HGA in urine and mutation analysis of the HGD gene. One of the differential diagnoses for the skin findings is exogenous ochronosis, a limited hyperpigmentation of skin caused by some chemicals. As for the lumbar spine findings, there can be radiographic similarities with ankylosing spondylitis (AS) including reduced intervertebral disc spaces and loss of lumbar lordosis; however, ochronosis will spare the sacroiliac joint, and the lumbar spine will show dense, wafer-like disk calcification with a vacuum disc phenomenon and broad syndesmophytes. Here, we present a case of a patient with probable ochronosis that was treated many years as ankylosing spondylitis without response, and we provide a review of the current literature on ochronosis pathogenesis, diagnosis, and treatment.
褐黄病和黑尿病是同一种疾病的表现——一种罕见的常染色体隐性遗传病，由先天性缺乏对映体-1,2-二氧酶（HGD）引起，导致对映体-邻苯二酚（HGA）的积累。在褐黄病中，HGA 会自动氧化和酶氧化，形成褐黄病色素，在软骨和结缔组织中积累。起初，会出现 HGA 尿症和软骨及其他结缔组织的色素沉着。多年后，脊柱和大关节的全身性骨关节炎，称为褐黄病性关节病，会发展。
通过对尿液中 HGA 的定量测量和 HGD 基因突变分析可以确诊。皮肤表现的鉴别诊断之一是外源性褐黄病，这是一种由某些化学物质引起的有限皮肤色素沉着。对于腰椎的发现，褐黄病与强直性脊柱炎（AS）可能有影像学相似之处，包括椎间盘间隙变窄和腰椎前凸减少；然而，褐黄病不会累及骶髂关节，腰椎会出现致密的、薄片状的椎间盘钙化，伴有真空椎间盘现象和广泛的韧带骨赘。在这里，我们介绍了一位可能患有褐黄病的患者，他多年来被误诊为强直性脊柱炎，且治疗无效，我们还对褐黄病的发病机制、诊断和治疗的当前文献进行了综述。
