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Alkaptonuria View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repositório Aberto da Universidade do Porto Alkaptonuria An obscure disease JOANA PEREIRA DA SILVA LAMAS DISSERTAÇÃO DE MESTRADO INTEGRADO EM MEDICINA 2016 [ALKAPTONURIA] P a g e | 2 Autor: Joana Pereira da Silva Lamas Orientador: Sara Isabel Mendes Rocha Assistente hospitalar de Medicina Interna no Centro Hospitalar do Porto – Hospital de Santo António Afiliação: Instituto de Ciências Biomédicas Abel Salazar Rua de Jorge Viterbo Ferreira nº 228 4050-313 PORTO [ALKAPTONURIA] P a g e | 3 ÍNDICE Abstract ..............................................................................................................................5 Resumo..............................................................................................................................6 Introduction ........................................................................................................................7 Materials and Methods ......................................................................................................8 History ................................................................................................................................9 Genetics and Metabolic Pathway ....................................................................................10 Epidemiology ...................................................................................................................13 Clinical Features and Natural History .............................................................................14 Homogentisic Aciduria ................................................................................................14 Ochronosis ..................................................................................................................14 Ochronotic Osteoarthropathy .....................................................................................16 Cardiovascular Manifestations ...................................................................................17 Genito-urinary Manifestations .....................................................................................18 Diagnosis .........................................................................................................................20 Therapies .........................................................................................................................21 Low Protein Diet..........................................................................................................21 Nitisinone ....................................................................................................................21 Complications from Nitisinone ...............................................................................22 Antioxidants ................................................................................................................23 Symptomatic Control ..................................................................................................24 Lifestyle Counselling ..............................................................................................24 Pain Control............................................................................................................24 Physiotherapy ........................................................................................................24 Ablative Laser Therapy ..........................................................................................25 Renal Replacement Therapy .................................................................................25 Other Options .........................................................................................................25 Surveillance ............................................................................................................25 Organ Transplantation ................................................................................................26 Future Therapies.........................................................................................................26 Prognosis .........................................................................................................................27 Conclusion .......................................................................................................................28 Resumo Circunstancial....................................................................................................29 Referências Bibliográficas ...............................................................................................36 [ALKAPTONURIA] P a g e | 4 LISTA DE ABREVIATURAS 4-HPPD – 4-hydroxyphenylpyruvate dioxygenase AA – Ascorbic acid AKU – Alkaptonuria BQA – Benzoquinone acetic acid HGA – Homogentisic acid HGD – Homogentisate 1,2-dioxygenase OOA – Ochronotic osteoarthropathy uHGA – Urinary homogentisic acid [ALKAPTONURIA] P a g e | 5 ALKAPTONURIA – an obscure disease Abstract Alkaptonuria (AKU) is a rare metabolic disease with an autosomal recessive inheritance. It is characterized by accumulation of homogentisic acid (HGA) as a consequence of the absence of the enzyme involved in the phenylalanine and tyrosine destruction pathway, homogentisate 1,2-dioxygenase (HGD). This deficiency results in accumulation in tissues and excretion of large quantities daily in urine of HGA, which are responsible for the triad of clinical features that characterized AKU: homogentisic aciduria, ochronosis and ochronotic osteoarthropathy. Usually, its earlier feature is the darkening of urine when exposed to air, which can be present since birth and is a consequence of homogentisic aciduria. Other systemic manifestations resulting from ochronosis and ochronotic osteoarthropathy are more recognizable around the fourth decade of life and thereafter. There is no currently approved cure for AKU, but nitisinone has been investigated as a potentially disease modifying therapy. Given these limitations, the symptomatic control of these patients is crucial and the most important approach, since AKU has a massive impact in patients’ quality of life. Greater efforts to improve recognition and diagnosis of the disease will be worthwhile and this review pretends to reunite all the information known until the present about AKU, mainly in what concerns its history, genetics and metabolic pathways, epidemiology, clinical features and natural history, diagnosis, therapies and prognosis. Therefore, this literature review is intended to disclose this entity, mainly to allow for early diagnosis and proper monitoring of these patients in an attempt to improve their quality of life. Keywords: alkaptonuria, ochronosis, ochronotic osteoarthropathy, homogentisic acid, homogentisate 1,2-dioxygenase [ALKAPTONURIA] P a g e | 6 Resumo A alcaptonúria é uma doença rara do metabolismo, de transmissão autossómica recessiva. Trata-se de uma aminoacidopatia que se caracteriza pela deficiência da enzima homogentisato 1,2-dioxidase, com acumulação subsequente de ácido homogentísico. A elevada excreção renal deste ácido e a sua deposição no tecido conjuntivo são responsáveis pela tríade associada à alcaptonúria de acidúria homogentísica, ocronose e osteoartropatia ocronótica. Habitualmente, a manifestação que aparece mais precocemente é o escurecimento de uma amostra de urina quando é deixada a repousar, característica esta que pode estar presente desde o nascimento e é consequência da acidúria homogentísica. As outras manifestações sistémicas de ocronose e osteoartropatia ocronótica surgem perto da quarta década de vida ou posteriormente. Atualmente não existe cura para a alcaptonúria, mas a nitisinona tem sido investigada como potencial terapêutica modificadora do curso da doença. Tendo em conta estas limitações, a abordagem terapêutica mais pertinente passa pelo controlo dos sintomas apresentados, que têm um grande impacto na qualidade de vida destes doentes. São necessários mais estudos para melhorar o reconhecimento e a suspeita da doença, pelo que esta dissertação tem como objetivo rever a bibliografia existente até à data sobre a alcaptonúria, nomeadamente no que diz respeito à sua história, genética e via metabólica, epidemiologia, manifestações clínicas e evolução natural, diagnóstico, tratamento e prognóstico. Assim, com esta revisão bibliográfica pretende-se divulgar esta entidade, sobretudo para que seja possível um diagnóstico precoce e um acompanhamento adequado destes doentes numa tentativa de melhorar a sua qualidade de vida. Palavras-chave: alcaptonúria, ocronose, osteoartropatia ocronótica, ácido homogentísico, homogentisato 1,2-dioxidase [ALKAPTONURIA] P a g e | 7 Introduction AKU is a rare metabolic disease of autosomal recessive inheritance. Reviewed by Sir Archibald Garrod in 1908, it was considered the disorder responsible for the creation and evolution of the inherited metabolic disease branch of medicine.1 The disease is a consequence from absence of HGD, an enzyme responsible for the conversion of HGA in maleylacetoacetic acid. Therefore, the deficiency of this enzyme results in accumulation of HGA in tissues and excretion of large quantities daily in urine, which are responsible for the triad of clinical features that characterize AKU: homogentisic aciduria, ochronosis and ochronotic osteoarthropathy (OOA).2 3 The disease has a systemic involvement, with cardiovascular, musculoskeletal, genito- urinary, ocular, cutaneous and respiratory manifestations.4
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