Long-term follow-up of alkaptonuria patients: single center experience

Objectives Alkaptonuria is a rare autosomal recessive genetic disorder resulting from the deficiency of homogentisate 1,2 dioxygenase (HGD), the third enzyme in the tyrosine degradation pathway. Homogentisic acid produced in excess oxidizes into ochronotic pigment polymer. Accumulation of this pigment in various tissues leads to systemic disease. Methods Clinical, laboratory, molecular findings and treatment characteristics of 35 patients followed up in Ege University Pediatric Nutrition, and Metabolism Department with the diagnosis of alkaptonuria were evaluated retrospectively. Results Twenty-four males (68.57%) and 11 females (31.42%) with a confirmed diagnosis of alkaptonuria from 32 different families were included in the study. We identified 11 different genetic variants; six of these were novel. c.1033C>T, c.676G>A, c.664G>A, c.731_734del, c.1009G>T, c.859_862delins ATAC were not previously reported in the literature. 24 (68.57%) patients only adhered to a low-protein diet in our study group. Seven (20%) patients initiated a low protein diet and NTBC therapy. Mean urinary HGA decreased by 88.7% with nitisinone. No statistical changes were detected in urinary HGA excretion with the low protein diet group. Conclusions In our study, alkaptonuria patients were diagnosed at different ages, from infancy to adulthood, and progressed with other systemic involvement in the follow-up. Since the initial period is asymptomatic, giving potentially effective treatment from an early age is under discussion. Raising disease awareness is very important in reducing disease mortality and morbidity rates.

Automated summary

This study retrospectively evaluated the clinical, laboratory, molecular findings, and treatment characteristics of 35 patients with alkaptonuria. The study found that 24 males and 11 females from 32 different families were diagnosed with alkaptonuria. The study also identified 11 different genetic variants, including 6 novel ones. The findings suggest that a low-protein diet can reduce urinary excretion of homogentisic acid.