Definition
Degenerative arthropathy due to Alkaptonuria
Metabolics
Rare hereditary disorder of tyrosine and phenylalanine breakdown
Homogentisic acid enzyme deficiency
- accumulate Homogentisic Acid
- product of tyrosine breakdown
Homogentisic acid deposited in cartilage & other soft tissues
- polymerises
- pathology probably due to a disruption of collagen cross links by metabolites of homogentisic acid
Clinical
Urine turns dark on standing
- also when alkalised
- hence the name
Sweat stains clothes
Cartilage & connective tissue stained grey
- brownish-black pigment in connective tissue
- calcified cartilage
- deposits in virtually all cartilages
- discs, sclera, skin
Arthropathy
- early OA secondary to brittleness
- presents 4th decade
- back pain then knees / shoulders / hips
- most common presenting complaint
Spondylosis
- especially affects spine
- difficult to differentiate from ankylosing spondylitis
- dense calcification of discs with narrowing of intervertebral space