Alkaptonuria, a Rare Genetic Disorder and its Molecular Basis (original) (raw)
Related papers
Natural History of Alkaptonuria
New England Journal of Medicine, 2002
Background Alkaptonuria, caused by mutations in the HGO gene and a deficiency of homogentisate 1,2-dioxygenase, results in an accumulation of homogentisic acid (HGA), ochronosis, and destruction of connective tissue. There is no effective therapy for this disorder, although nitisinone inhibits the enzyme that produces HGA. We performed a study to delineate the natural history of alkaptonuria. Methods We evaluated 58 patients with alkaptonuria (age range, 4 to 80 years), using clinical, radiographic, biochemical, and molecular methods. A radiographic scoring system was devised to assess the severity of spinal and joint damage. Two patients were treated with nitisinone for 10 and 9 days, respectively. Results Life-table analyses showed that joint replacement was performed at a mean age of 55 years and that renal stones developed at 64 years, cardiacvalve involvement at 54 years, and coronary-artery calcification at 59 years. Linear regression analysis indicated that the radiographic score for the severity of disease began increasing after the age of 30 years, with a more rapid increase in men than in women. Twenty-three new HGO mutations were identified. In a 51-year-old woman, urinary HGA excretion fell from 2.9 to 0.13 g per day after a 10-day course of nitisinone (7 days at a dose of 0.7 mg per day and 3 days at 2.8 mg per day). In a 59-year-old woman, urinary HGA fell from 6.4 g to 1.7 g per day after nine days of treatment with nitisinone (0.7 mg per day). Plasma tyrosine levels in these patients rose from approximately 1.1 mg per deciliter (60 µmol per liter) in both to approximately 12.8 mg per deciliter (700 µmol per liter) and 23.6 mg per deciliter (1300 µmol per liter), respectively, with no clinical signs or symptoms. Conclusions The reported data on the natural history of alkaptonuria provide a basis for the evaluation of long-term therapies. Although nitisinone can reduce HGA production in humans with homogentisate 1,2-dioxygenase deficiency, the long-term safety and efficacy of this treatment require further evaluation.
Genetics of alkaptonuria – an overview
Acta Facultatis Pharmaceuticae Universitatis Comenianae, 2015
Alkaptonuria (AKU) is the first described inborn error of metabolism and a classical example of rare autosomal recessive disease. AKU patients carry homozygous or compound heterozygous mutations of the gene coding for enzyme homogentisate dioxygenase (HGD) involved in metabolism of tyrosine. The metabolic block in AKU causes accumulation of homogentisic acid (HGA) that, with advancing age of the patient, leads to severe and painful ochronotic arthropathy.
Alkaptonuria: Current Perspectives
The Application of Clinical Genetics
The last 15 years have been the most fruitful in the history of research on the metabolic disorder alkaptonuria (AKU). AKU is caused by a deficiency of homogentisate dioxygenase (HGD), the enzyme involved in metabolism of tyrosine, and is characterized by the presence of dark ochronotic pigment in the connective tissue that is formed, due to high levels of circulating homogentisic acid. Almost 120 years ago, Sir Archibald Garrod used AKU to illustrate the concept of Mendelian inheritance in man. In January 2019, the phase III clinical study SONIA 2 was completed, which tested the effectiveness and safety of nitisinone in the treatment of AKU. Results were positive, and they will serve as the basis for the application for registration of nitisinone for treatment of AKU at the European Medicines Agency. Therefore, AKU might become a rare disease for which a cure will be found by 2020. We understand the natural history of the disease and the process of ochronosis much more, but at the same time there are still unanswered questions. One of them is the issue of the factors influencing the varying severity of the disease, since our recent genotype-phenotype study did not show that differences in residual homogentisic acid activity caused by the different mutations was responsible. Although nitisinone has proved to arrest the process of ochronosis, it has some unwanted effects and does not cure the disease completely. As such, enzyme replacement or gene therapy might become a new focus of AKU research, for which a novel suitable mouse model of AKU is available already. We believe that the story of AKU is also a story of effective collaboration between scientists and patients that might serve as an example for other rare diseases.
A rare case of metabolic disorder- Alkaptonuria
Journal of Case Reports and Scientific Images, 2021
Alkaptonuria is a rare genetic disorder of tyrosine metabolism, due to deficiency of the enzyme homogentisate 1, 2 dioxygenase. This results in characteristic features like blackish urine discoloration, ochronosis, arthropathy, cardiac valve deterioration. In this paper, the authors presenta case report of a 4-month-old boy who was brought by his mother to the well-baby clinic, with a chief complaint of black staining of nappy, a few hours after voiding. A qualitative examination of urine after an hour of the collection showed dark black discoloration, Quantitative examination reveals the presence of homogentisic acid to the extent of200mg/dl. The Diagnosis of Alkaptonuria was confirmed and the infant was started on Vitamin C and put under regular follow-up.
Alkaptonuria, more than just a mere disease
Journal of Neurosciences in Rural Practice, 2015
ABSTRACTAlkaptonuria (AKU) is considered a rare autosomal recessive condition that results in an accumulation of homogentisic acid in body tissues and causes long-term clinical, neurological and psychological complications. We present a comprehensive evaluation of an atypical 46-year-old Caucasian male who developed all clinical diagnostic symptoms of AKU (ochronotic pigmentations, dark urine and clinical arthritis of major joints including spine) by 25 years of age, well before the typical age mentioned in many reviews. First signs of ochronotic ear pigmentations unexpectedly started appearing as early as 12 years of age. A long “disease-free” period typical in classical AKU patient was also absent. This case report highlights the importance of considering psychological issues in AKU patients. The patient showed symptoms of dysthymia reporting social isolation, diminished interest in pleasurable activities, feeling of worthlessness and irritability as major psychological issues. Ea...
Sequence analysis of the homogentisate 1,2 dioxygenase gene in a family affected by alkaptonuria
Journal of medical genetics, 1999
Sequence analysis of the homogentisate 1,2 dioxygenase gene in a family aVected by alkaptonuria EDITOR-Alkaptonuria (AKU) is a disorder of the catabolism of aromatic amino acids. A defect of homogentisate 1,2 dioxygenase (HGO) leads to an accumulation of homogentisic acid (HGA) and subsequently to deposition of polymerised HGA, a brown-black pigment, in connective tissue, primarily in cartilage. 1 2 This phenomenon is known as ochronosis. It results in debilitating arthropathy which typically becomes manifest in the fourth decade of life. Large amounts of HGA are excreted in the urine and cause its black discolouration upon oxidation. In 1891, homogentisic acid was first isolated by Wolkow and Baumann 3 from the urine of an AKU patient from a remote area of the Black Forest in south western Germany. In 1902, Garrod, aware of this biochemical finding, observed the autosomal recessive mode of inheritance of AKU and thereby showed for the first time that mendelian laws also apply to human genetics. 4 Garrod postulated that AKU results from an enzyme deficiency and introduced the concept of the "inborn error of metabolism". 5 Recently, the human gene encoding HGO was cloned by Fernádez-Cañón et al. 6 Two diVerent mutations of this gene were identified in two unrelated AKU aVected families. These mutations cosegregated with manifest disease and could be shown to abrogate enzymatic activity of HGO protein. 6 Homozygosity for these mutations, therefore, was the cause of AKU in the two families. Two additional mutations in the HGO gene were found to cosegregate with AKU in two Slovakian pedigrees. 7 One of these mutations caused a frameshift in an upstream exon and was thus likely to result in a loss of HGO activity. For an additional mutation, complete cosegregation with AKU was reported in an extensively studied Canarian family. 8 Various diVerent mutations of the HGO gene were found in 14 unrelated AKU patients. 9 We performed sequence analysis of the HGO gene in an AKU aVected family from the Black Forest. AKU with severe ochronosis including involvement of the sclerae was diagnosed at necropsy of a 71 year old farmer (fig 1, No 1). The diagnosis of AKU had not been established during the patient's lifetime. He died of recurrent myocardial infarction. Subsequently, the patient's family underwent physical examination. A sister (fig 1, No 2) and a first cousin (fig 1, No 3) were found to be aVected by the disease. These patients have been suVering from arthritic symptoms of AKU since the fourth decade of life and show the typical discolouration of the urine and the ochronotic pigmentation of the sclerae. However, the condition had until then been misdiagnosed as degenerative polyarthritis. A brother (fig 1, No 4) of patient 1 was healthy as were the three children (fig 1, Nos 5, 6, and 7) of patient 2. Anamnestically, a brother (fig 1, No 8) and a first cousin (fig 1, No 9), who died in 1988 and 1995, respectively, were reported to have suVered from debilitating early onset polyarthropathy and the typical ochronotic involvement of the sclerae. They were very probably affected by AKU. No characteristic AKU symptoms were reported
2012
Alkaptonuria (AKU) is characterised by a typical bluish-black pigmentation in connective tissue (ochronosis) that usually occurs after the age of 30 years. AKU is the first inborn error of metabolism to be understood as a recessive trait. It is caused by mutations within the gene located on the human chromosome 3q13.33, coding for the enzyme homogentisate 1,2-dioxygenase (HGD). About 650 AKU patients have been reported worldwide, and mutation analysis performed so far in about 270 cases shows a rather high heterogeneity, since 117 AKU-causing mutations have been found, also summarized in a novel HGD mutation database. Several ethnicities have been reported in which an increased incidence of AKU is observed, compared to its worldwide low prevalence (1 : 250 000 – 1 : 1 000 000). S t r e s z c z e n i e
Nine cases of Alkaptonuria in one family in southern Jordan
Rheumatology International, 2012
Alkaptonuria is a rare autosomal recessive metabolic disorder characterized by a deficiency of homogentisate 1,2-dioxygenase (HGO) in the liver. This results in excretion of large quantities of homogentisic acid (HGA) (also called alkapton) in the urine and a slowly progressive deposition of homogentisic acid and its oxidative product in connective tissues. Clinical characteristic features of alkaptonuria are darkening of urine, bluish-dark pigmentation of connective tissues (ochronosis) and arthritis of large joints and spine. Cardiovascular and genitourinary systems may also be affected. In this report, we present the initial results of screening family members with history of alkaptonuria in southern region of Jordan. We present 9 cases of alkaptonuria (two males and seven females) in one Jordanian family. The history, signs and symptoms, diagnostic techniques and treatment options of alkaptonuria are reviewed in this article.
A Previously Undiagnosed Case of Alkaptonuria: A Case Report
Turkish Journal of Rheumatology, 2013
Alkaptonüri, idrardan çok miktarda homogentisik asit atılımı, okronozis ve omurga ve büyük eklemlerde tahrip edici artrit ile karakterize, fenilalanin ve tirozin katabolik yolağında nadir görülen bir metabolik bozukluktur. Birçok etnik grupta çok nadir görülse de, Slovakya ve Dominik Cumhuriyeti gibi bazı ülkelerde daha sık karşılaşılır. Bu yazıda, alkaptonürinin ileri klinik özelliklerini taşıyan 58 yaşında Ürdünlü bir kadın olgu sunuldu. Anahtar sözcükler: Alkaptonüri; artrit; koyu idrar; homogentisik asit; pigmentasyon. Alkaptonuria is a rare metabolic disorder in the phenylalanine and tyrosine catabolic pathway which is characterized by the excessive excretion of homogentisic acid in the urine, ochronosis, and debilitating arthritis of the spine and large joints. Although it is a very rare disease in most ethnic groups, it is more common in some countries, such Slovakia and the Dominican Republic. In this report, we report a 58-year-old Jordanian female case with advanced clinical features of alkaptonuria.