Demographic, Phenotypic and Genotypic Features of Alkaptonuria Patients: A Single Centre Experience

Abstract

Aim:Alkaptonuria (AKU) is an autosomal recessively inherited disease caused by a deficiency of homogentisate 1,2-dioxygenase. This enzyme converts homogentisic acid (HGA) into maleylacetoacetic acid in the tyrosine degradation pathway. The presence of HGA in urine, ochronosis (bluish-black pigmentation in connective tissues) and arthritis of the spine and the other large joints are the three major features of AKU. Nitisinone and a tyrosine-restricted diet are the treatment options. In this study, we evaluated the demographic and clinical characteristics and also the mutations of our AKU patients.Materials and Methods:This retrospective single centre study included 36 patients who were diagnosed as AKU between the years of 2002 and 2017 Çukurova University Faculty of Medicine, Department of Pediatrics, Division of Metabolism and Nutrition.Results:Thirty six AKU patients were included (17 female, 19 male) in our study. The mean age of the patients was 9.3±13.4 years (3 months-54 years). The major complaints were darkening of the urine (100%), ochronosis (11.1%), arthralgia (16.7%) and arthritis (8.1%). Darkening of the urine was firstly recognized at the age of 8.89±16.9 months (1-84 months). Eighteen (86%) patients had homozygous and 3 (14%) patients had compound heterozygous mutations in the HGD gene.Conclusion:AKU was the first inherited metabolic disease defined. The three main features are; darkening of the urine at birth which is followed by ochronosis (blue-dark pigmentation) clinically visible in the ear and alae of the nose and finally a severe ochronotic arthropathy of the spine and large joints at around the age of 50 years. Here we report on the clinical and genetic features of our patients at various ages.

Keywords

• Alkaptonuria
• ochronosis
• homogentisic acid
• homogentisate 1
• 2 dioxygenate
• arthritis