system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Which of the following conditions is associated with darkening of urine on standing?
assistant
The correct answer is  Characteristic sign of alkaptonuria is darkening of urine on standing, especially if the urine is alkaline. Ref: Harrison's 16th Edition, Page 2334; Essential Pediatrics, OP Ghai - 6th Edition, Page 610; Nelson's Paediatrics 17th Edition, Page 403; Lippincotts 3rd Edition, Page 272.