A 28-year-old Indian male presents with a 10-year history of progressive darkening of his urine, which turns black upon standing or exposure to air. He has recently developed arthralgia in his knees and lower back. On examination, there is a dark pigmentation of the sclera and ear cartilage. His urine is dark brown-black and gives a dark precipitate with ferric chloride. Serum creatinine is normal. What is the most likely diagnosis?