ICD-11 definition : Alkaptonuria is characterised by the accumulation of homogentisic acid (HGA) and its
oxidised product benzoquinone acetic acid (BQA), leading to a darkening of the urine
when it is left exposed to air, grey-blue colouration of the eye sclerae and the ear
helix (ochronosis), and a disabling joint disease involving both the axial and peripheral
joints (ochronotic arthropathy).;
Alkaptonuria is characterised by the accumulation of homogentisic acid (HGA) and its
oxidised product benzoquinone acetic acid (BQA), leading to a darkening of the urine
when it is left exposed to air, grey-blue colouration of the eye sclerae and the ear
helix (ochronosis), and a disabling joint disease involving both the axial and peripheral
joints (ochronotic arthropathy).