| • | autosomal recessive; presents in childhood (dark cerumen, and blackstained underwear after washing) |
pathogenesis:
| • | deficiency of homogentisic acid oxidase with secondary accumulation of homogentisic acid in connective tissue |
clinical:
| • | blue-gray pigmented cartilage and tendons visualized through the skin on ears, nose tip, extensor hands |
| • | brown/black cerumen, sweat |
| • | severe arthropathy involving large joints |
| • | dark urine when pH above 7.0 (diapers, clothing discolored after cleansing with alkaline soaps) |
| • | ddx: exogenous ochronosis (antimalarials, hydroquinone), argyria, chrysoderma, amiodarone |
labs:
| • | enzyme assay – measurement of urinary homogentisic acid |
| • | darkening of urine with addition of NaOH |
|