A mother reports that her infant's diapers stain black after washing and the urine darkens on standing. The child is developmentally normal. In adulthood this patient is most likely to develop which complication?

• A Hepatocellular carcinoma
• B Cherry-red spot with progressive dementia
• C Recurrent uric acid nephrolithiasis
• D Ochronotic arthropathy of the spine and large joints ✓

Explanation

Alkaptonuria, caused by homogentisic acid oxidase deficiency, leads to excretion of homogentisic acid, which oxidizes and polymerizes to a dark pigment on standing. It was the first described inborn error of metabolism by Garrod. Pigment deposits in cartilage cause ochronosis, with degenerative arthropathy of the spine and large joints in adulthood, plus dark pigmentation of ear and nose cartilage. Intelligence remains normal, distinguishing it from the storage disorders listed among the distractors.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.