ABSTRACT
Alkaptonuria (AKU) is a very rare autosomal recessive disorder of tyrosine metabolism in the liver due to deficiency of homogentisate 1,2 dioxygenase (HGD) activity, resulting in the accumulation of homogentisic acid (HGA). Circulating HGA pass into various tissues through-out the body, mainly in cartilage and connective tissues, where its oxidation products polymerize and deposit as a melanin-like pigment. Gram quantities of HGA are excreted in the urine. AKU is a progressive disease and the three main features, according the chronology of appearance, are: darkening of the urine at birth, then ochronosis (blue-dark pigmentation of the connective tissue) clinically visible at around 30 yrs in the ear and eye, and finally a severe ochronotic arthropathy at around 50 yrs with spine and large joints involvements. Cardiovascular and renal complications have been described in numerous case report studies. A treatment now is available in the form of a drug nitisinone, which decreases the production of HGA. The enzymatic defect in AKU is caused by the homozygous or compound heterozygous mutations within the HGD gene. This disease has a very low prevalence (1:100,000-250,000) in most of the ethnic groups, except Slovakia and Dominican Republic, where the incidence has shown increase up to 1:19,000. This review highlights classical and recent findings on this very rare disease.
Subject(s)
Alkaptonuria/complications , Alkaptonuria/genetics , Alkaptonuria/metabolism , Alkaptonuria/therapy , Homogentisic Acid/metabolism , Humans , Melanins/biosynthesis , Ochronosis/complicationsABSTRACT
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.