Alkaptonuria in Russia.

Alkaptonuria is characterized by the accumulation of homogentisic acid (HGA), part of which is excreted in the urine but the excess HGA forms a dark brown ochronotic pigment that deposits in the connective tissue (ochronosis), eventually leading to early-onset severe arthropathy. We analyzed a cohort of 48 Russian AKU families by sequencing all 14 exons (including flanking intronic sequences) of the homogentisate 1,2-dioxygenase gene (HGD) and Multiplex Ligation-dependent Probe Amplification (MLPA) analysis. Nine novel likely pathogenic HGD variants were identified, which have not been reported previously in any other country. Recently, Bychkov et al. [1] reported on the variant spectrum in another cohort of 49 Russian AKU patients. Here we summarize complete data from both cohorts that include 82 Russian AKU families. Taken together, 31 different HGD variants were found in these patients, of which 14 are novel and found only in Russia. The most common variant was c.481G>A (p.(Gly161Arg)), present in almost 54% of all AKU alleles.

A molecular spectroscopy approach for the investigation of early phase ochronotic pigment development in Alkaptonuria.

Alkaptonuria (AKU), a rare genetic disorder, is characterized by the accumulation of homogentisic acid (HGA) in organs due to a deficiency in functional levels of the enzyme homogentisate 1,2-dioxygenase (HGD), required for the breakdown of HGA, because of mutations in the HGD gene. Over time, HGA accumulation causes the formation of the ochronotic pigment, a dark deposit that leads to tissue degeneration and organ malfunction. Such behaviour can be observed also in vitro for HGA solutions or HGA-containing biofluids (e.g. urine from AKU patients) upon alkalinisation, although a comparison at the molecular level between the laboratory and the physiological conditions is lacking. Indeed, independently from the conditions, such process is usually explained with the formation of 1,4-benzoquinone acetic acid (BQA) as the product of HGA chemical oxidation, mostly based on structural similarity between HGA and hydroquinone that is known to be oxidized to the corresponding para-benzoquinone. To test such correlation, a comprehensive, comparative investigation on HGA and BQA chemical behaviours was carried out by a combined approach of spectroscopic techniques (UV spectrometry, Nuclear Magnetic Resonance, Electron Paramagnetic Resonance, Dynamic Light Scattering) under acid/base titration both in solution and in biofluids. New insights on the process leading from HGA to ochronotic pigment have been obtained, spotting out the central role of radical species as intermediates not reported so far. Such evidence opens the way for molecular investigation of HGA fate in cells and tissue aiming to find new targets for Alkaptonuria therapy.

Variant Analysis of Alkaptonuria Families with Significant Founder Effect in Jordan.

BACKGROUND: Metabolic disorder alkaptonuria is an autosomal recessive disorder caused by mutations in the HGD gene, and a deficiency HGD enzyme activity results in an accumulation of homogentisic acid (HGA), ochronosis, and destruction of connective tissue. METHODS: We clinically evaluated 18 alkaptonuria patients (age range, 3 to 60 years) from four unrelated families. Furthermore, 11 out of 18 alkaptonuria patients and 7 unaffected members were enrolled for molecular investigations by utilizing Sanger sequencing to identify variants of the 14 exons of HGD gene. RESULTS: We found that the seven patients from the 4 unrelated families carried a recurrent pathogenic missense variant (c.365C>T, p. Ala122Val) in exon 6 of HGD gene. The variant was fully segregated with the disease in affected family members while the other unaffected family members were heterozygous carriers for this variant. Additionally, the clinical features were fully predicted with alkaptonuria disorder. CONCLUSION: In this study, we confirmed that the most common variants in Jordanian AKU patients was c.365C>T, p. Ala122Val in exon 6 of HGD gene. Additionally, we correlated the clinical and genetic features of AKU patients at various ages (3-60 years).

Alcaptonúria (ocronose): relato de caso de irmãos / Alkaptonuria (ochronosis): a case report of siblings

A Alcaptonúria é uma doença autossômica recessiva rara caracterizada pelo acúmulo de ácido homogentísico. Denomina-se também ocronose e manifesta-se por pigmentação azulada de tecidos orgânicos e urina enegrecida, além de artropatia. A seguir, será relatado o caso de irmãos portadores de artropatia ocronótica e a conduta ortopédica (AU)

Alkaptonuria is a rare autosomal recessive disease characterized by the accumulation of homogentisic acid. It is also called ochronosis and is manifested by bluish pigmentation of organic tissues and blackened urine, besides arthropathy. Here the authors report the case of siblings with ochronotic arthropathy and the orthopedic management (AU)

Ochronotic involvement of the aortic and mitral valves in a 72-year-old man.

Ochronosis, an autosomal recessive metabolic disorder, causes an excess of homogentisic acid that results in adverse pigmentation, calcification, and inflammation of cartilaginous and other tissues. Cardiovascular abnormalities are less frequently reported than are other manifestations. In rare cases, ochronosis can cause valvular heart disease. We report the case of a 72-year-old man with aortic stenosis and mitral insufficiency who was diagnosed with ochronosis while undergoing surgical aortic and mitral valve replacement. We discuss the history and surgical management of alkaptonuric ochronosis.

Ochronotic osteoarthropathy in a mouse model of alkaptonuria, and its inhibition by nitisinone.

BACKGROUND: Alkaptonuria (AKU) is a rare metabolic disease caused by deficiency of homogentisate 1,2 dioxygenase, an enzyme involved in tyrosine catabolism, resulting in increased circulating homogentisic acid (HGA). Over time HGA is progressively deposited as a polymer (termed ochronotic pigment) in collagenous tissues, especially the cartilages of weight bearing joints, leading to severe joint disease. OBJECTIVES: To characterise blood biochemistry and arthropathy in the AKU mouse model (Hgd-/-). To examine the therapeutic effect of long-term treatment with nitisinone, a potent inhibitor of the enzyme that produces HGA. METHODS: Lifetime levels of plasma HGA from AKU mice were measured by high-performance liquid chromatography (HPLC). Histological sections of the knee joint were examined for pigmentation. The effect of nitisinone treatment in both tissues was examined. RESULTS: Mean (±SE) plasma HGA levels were 3- to 4-fold higher (0.148±0.019 mM) than those recorded in human AKU. Chondrocyte pigmentation within the articular cartilage was first observed at 15 weeks, and found to increase steadily with mouse age. Nitisinone treatment reduced plasma HGA in AKU mice throughout their lifetime, and completely prevented pigment deposition. CONCLUSIONS: The AKU mouse was established as a model of both the plasma biochemistry of AKU and its associated arthropathy. Early-stage treatment of AKU patients with nitisinone could prevent the development of associated joint arthropathies. The cellular pathology of ochronosis in AKU mice is identical to that observed in early human ochronosis and thus is a model in which the early stages of joint pathology can be studied and novel interventions evaluated.

Aortic valve disease as a first manifestation of Alcaptonuria in surgically treated patient. Case report.

BACKGROUND: Alcaptonuria, a rare metabolic disorder (1:250 000), is usually presented with symptoms such as arthropathies of weight bearing joints. CASE REPORT: In this case, a 65 year old woman was admitted to our hospital with severe aortic stenosis and no other symptoms that would suggest the existance of Alcaptonuria. Intraoperative findings of black discoloration of the affected valve and ascending aorta, pointed towards the diagnosis of cardiac ochronosis, what was then confirmed by a PH examination. CONCLUSION: This case suggests that although alcaptonuria is a slow progressive disease with cardiac ochronosis as a predictable late complication, it can nevertheless be a first sign. In that case the attention should be brought to the surely affected lumbar spine and weight bearing joints, and other connective tissue. KEY WORDS: Alcaptonuria, Aortic valve, Cardiac ochronosis, Surgery.

Biochemical and proteomic characterization of alkaptonuric chondrocytes.

Alkaptonuria (AKU) is a rare genetic disease associated with the accumulation of homogentisic acid (HGA) and its oxidized/polymerized products which leads to the deposition of melanin-like pigments (ochronosis) in connective tissues. Although numerous case reports have described ochronosis in joints, little is known on the molecular mechanisms leading to such a phenomenon. For this reason, we characterized biochemically chondrocytes isolated from the ochronotic cartilage of AKU patients. Based on the macroscopic appearance of the ochronotic cartilage, two sub-populations were identified: cells coming from the black portion of the cartilage were referred to as "black" AKU chondrocytes, while those coming from the white portion were referred to as "white" AKU chondrocytes. Notably, both AKU chondrocytic types were characterized by increased apoptosis, NO release, and levels of pro-inflammatory cytokines. Transmission electron microscopy also revealed that intracellular ochronotic pigment deposition was common to both "white" and "black" AKU cells. We then undertook a proteomic and redox-proteomic analysis of AKU chondrocytes which revealed profound alterations in the levels of proteins involved in cell defence, protein folding, and cell organization. An increased post-translational oxidation of proteins, which also involved high molecular weight protein aggregates, was found to be particularly relevant in "black" AKU chondrocytes.

Degenerative arthritis of the knee secondary to ochronosis.

Alkaptonuria is a rare disease in which a deficiency in the homogentisate 1, 2-dioxygenase enzyme results in a buildup of homogentisic acid. Ochronosis, the deposition of excess homogentisic acid in connective tissue, causes brownish-black pigmentation and weakening of the tissue ultimately resulting in chronic inflammation, degeneration, and osteoarthritis. There is currently no definitive cure for alkaptonuric ochronosis, and management is usually symptomatic. However, total joint replacements in severe cases of ochronotic osteoarthritis have comparable outcomes to osteoarthritic patients without ochronosis. We report a case of a patient with ochronotic arthritis of the knee treated with total knee arthroplasty.

An update on molecular genetics of Alkaptonuria (AKU).

Alkaptonuria (AKU) is an autosomal recessive disorder caused by a deficiency of homogentisate 1,2 dioxygenase (HGD) and characterized by homogentisic aciduria, ochronosis, and ochronotic arthritis. The defect is caused by mutations in the HGD gene, which maps to the human chromosome 3q21-q23. AKU shows a very low prevalence (1:100,000-250,000) in most ethnic groups, but there are countries such as Slovakia and the Dominican Republic in which the incidence of this disorder rises to as much as 1:19,000. In this work, we summarize the genetic aspects of AKU in general and the distribution of all known disease-causing mutations reported so far. We focus on special features of AKU in Slovakia, which is one of the countries with an increased incidence of this rare metabolic disorder.

[Ochronosis: report of two familial cases]. / L'ochronose: a propos de deux cas familiaux.

BACKGROUND: Ochronosis of alkaptonuria is a rare hereditary autosomal recessive disease in which there is an absence of homogentisic acid oxidase resulting in accumulation of homogentisic acid in tissues. AIM: To report a new case of alkaptonuria CASE REPORT: A 49-year-old man had been followed for 4 years for chronic lombalgia and arthropaty of two knees. He is married to his cousin and father of 4 girls. His parents are also cousins. The clinical examination has found a cutaneuous pigmentation and a lumbar stiffness. At biological checking, creatininemia was at 190 µmol/L and there are not inflammatory indicators. The radiography have shown a discal dorsolumbar calcifications, anterior inter somatic bridges and bilateral arthritis of knees without articular chondrocalcinosis. The diagnosis of ochronosis have been suspected and confirmed by the blackness of urine and the dosage of alkaptonuria. The patient has been treated symptomatiquely. Familial investigation have revealed that his daughter suffered from the same disease with the notion of blackness of urine. She is 12 year old and she's asymptomatic on the osteoarticular level. CONCLUSION: Alkaptonuria causes a degenerative arthropaty which can endanger functional prognosis. Early diagnosis and scanning of this innate error of metabolism by genetic study play a fundamental interest, especially for molecular and genetic advisement.

Familiar ochronotic arthropathy-caused by a gene mutation traced three hundred years.

Authors trace an ochronotic Hungarian family, which moved from Slovakia to Hungary 300 years ago. As the family members lived in a relatively close village community the gene mutation had been survived silently for ages before the clinical symptoms developed. Family tree analysis could detect with the use of allele specific PCR amplification-the p.G161R mutation of the homogentisic acid 1,2-dioxygenase (HGD) gene, which resulted in a specific genotype appearing in the Slovak population. We found a heterozygote member of this family who has children with an alkaptonuria-homozygote and known-heterozygote genotypes so there would be a high risk of alkaptonuria in their offsprings. Therefore genetic counselling is highly recommended to minimize the risk factors.

[Osteoarthritis in hereditary metabolic diseases]. / Arthrosen bei hereditären Stoffwechselerkrankungen.

Primary osteoarthritis (OA) of peripheral joints is a common disease mainly occurring after the age of 50. It is important to distinguish primary from secondary OA. Younger age at disease onset, rapid progression, unusual disease manifestations and co-morbidities are signs of secondary OA. This review outlines an important group of secondary OA. Hereditary metabolic diseases can exhibit joint involvement. For some of these diseases, correct diagnosis is critical, since appropriate therapy influences not only joint function and quality of life, but can also prevent relevant end-organ damage.

Acute anterior uveitis as the initial presentation of alkaptonuria.

Alkaptonuria is a rare autosomal recessive metabolic disorder that may present with multi-system involvement such as ochronotic arthropathy, renal, urethral and prostatic calculi, cardiac valvular lesions and pigmentation of the skin, sclera, cartilage and other connective tissues. An association of the disease with uveitis has never been reported. We report the first case of alkaptonuria with ochronotic arthropathy presenting with recurrent acute anterior uveitis as the initial manifestation. The possible common link with the HLA-B27 gene is discussed.

Three-generational alkaptonuria in a non-consanguineous family.

OBJECTIVE: Alkaptonuria (AKU) is a rare inborn error of metabolism of aromatic amino acids and considered to be an autosomal recessive trait caused by mutations in the homogentisate 1,2-dioxygenase (HGD) gene. A dominant pattern of inheritance has been reported but was attributed to extended consanguinity in many cases. However, we have observed a non-consanguineous family segregating AKU in a dominant manner over three generations. RESULTS: All affected individuals presented with typical features of AKU including darkening of the urine, ochronosis, arthropathy, and elevated urinary excretion of homogentisic acid. Sequence analysis of the HGD gene from genomic DNA of two affected individuals, uncle and niece, revealed a heterozygous missense mutation (M368V) in the uncle that was not present in his niece. Microsatellite genotyping demonstrated that both were heterozygous at the HGD locus and shared one haplotype. This haplotype did not contain a detectable HGD mutation. The haplotype was also found in a healthy son of the niece, making a dominant HGD mutation unlikely. Moreover, sequencing of cDNA from lymphoblastoid cells of the niece did not reveal an HGD mRNA with a potentially dominant-negative effect. CONCLUSION: Rare causes of the uncommon AKU inheritance in this family have to be considered, ranging from the coincidence of undetectable HGD mutations to a dominant mutation of a second, hitherto unknown AKU gene.

Coexistence of ochronosis and B 27 positive ankylosing spondylitis.

We describe a 49-year-old man with coexistence of ochronosis and B27 positive ankylosing spondylitis. This is the first report documenting the simultaneous occurrence of ochronosis and B27 positive ankylosing spondylitis, with no positive familiar history for seronegative spondylarthropathies. The relations of these rheumatic diseases are discussed.

Alkaptonuria, ochronosis, and ochronotic arthropathy.

OBJECTIVES: To describe the clinical presentation and course of a relatively large group of Italian adult patients screened for mutation of the homogentisate dioxygenase gene causing alkaptonuria (AKU) and ochronosis, and to review typical and atypical facets of this condition. METHODS: We reviewed the medical records of 9 patients affected by ochronotic arthropathy who were observed in our institutions between 1979 and 2001. All patients were diagnosed as having AKU through a rapid urine test with alkali. Mutation screening was performed by single-strand conformation analysis of all homogentisate dioxygenase exons, followed by sequencing of altered conformers. RESULTS: Our 9 cases had similar clinical features and they reflected those described in the literature: a progressive degenerative arthropathy mainly affecting axial and weight-bearing joints associated with extraarticular manifestation. Musculoskeletal symptoms began in most of our patients around the age of 30 years with back pain and stiffness: involvement of the large peripheral joints usually occurred several years after spinal changes. Ochronotic peripheral arthropathy generally was degenerative, but joint inflammation was observed in some cases; this could be attributed to an inflammatory reaction of the ochronotic shard in the synovial membrane. CONCLUSIONS: Ochronosis is a model of arthropathy with known etiologic factors. Over time, AKU, the genetically determined metabolic defect, leads to the accumulation of pigment and the development of this crippling condition. Most of the clinical findings may be explained by inhibition of collagen crosslinks, but some require additional interpretation. For example, inflammatory features of the ochronotic joint only occur in a minority of cases, and may be attributable to ochronotic shards. Further studies are needed to establish the genotype-phenotype correlation to identify mutations that are predictive of severe disease. For this purpose, the Italian Study Group on Alkaptonuria (www.dfc.unifi.it/aku) is enrolling affected patients in an on-line database to characterize the molecular defects and their relationship to clinical data.