Secondary osteoarthritis due to alkaptonuria: a case report

Abstract

Background & Aims: Alkaptonuria is a rare autosomal recessive genetic disorder caused by a deficiency of homogentisate 1,2-dioxygenase, leading to the accumulation of homogentisic acid. It presents with a characteristic triad of homogentisic aciduria, ochronosis, and progressive arthritis, often resulting in secondary osteoarthritis, particularly affecting the hip and knee joints. Case Description: A 58-year-old male presented with severe pain in the right hip and left shoulder. Since childhood, his urine had turned black upon exposure to sunlight. His medical history included multiple fractures and orthopedic interventions. On clinical examination, bluish-black discoloration of the ear lobes and sclera was noted. Biochemical testing, including Benedict’s test, ammoniacal silver nitrate test, and a filter paper spot test using 10% sodium hydroxide, confirmed the diagnosis of alkaptonuria. The patient was diagnosed with osteoarthritis secondary to alkaptonuria and underwent a successful total hip replacement. Conclusion: Early diagnosis and intervention in alkaptonuria are crucial to preventing the debilitating effects of secondary osteoarthritis. A multidisciplinary approach in the management of patients with alkaptonuria can help reduce morbidity and improve quality of life by addressing both symptoms and the underlying disease.

Keywords

• alkaptonuria
• ammoniacal silver nitrate test
• homogentisic acid
• ochronotic arthropathy