Parents report that their infant's cloth diapers stain black after washing. The child is otherwise developing normally. In adulthood, this child is most likely to develop which complication?

• A Progressive cardiomyopathy
• B Recurrent calcium oxalate renal stones
• C Cherry-red retinal spot with blindness
• D Pigmentation of cartilage with degenerative arthritis ✓

Explanation

Alkaptonuria, due to homogentisic acid oxidase deficiency, is a benign disorder of tyrosine catabolism in childhood whose only early sign is darkening of urine on standing or black-stained diapers. Oxidised homogentisic acid polymerises and binds collagen, producing ochronotic pigmentation of cartilage, sclerae, and ear, and degenerative arthropathy of the spine and large joints in adult life. It does not cause stones, retinal changes, or cardiomyopathy.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.