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Definition
Cause
- Enzyme deficiency
- Due to rare hereditary disorder of tyrosine and phenylalanine degradation
- Have absence of homogentisic acid oxidase leading to accumulation of homogentisic acid throughout body
- Deposits in virtually all collagen containing tissues over time
- Discs, cartilage, sclera, skin leading to Spondylosis, arthropathy
- Probably due to a disruption of collagen cross links by metabolites of homogentisic acid
- results in Accumulate Homogentisic Acid
- Product Tyrosine breakdown
- Deposited in cartilage & other soft tissues
- Polymerises
- Excreted in urine
- Urine turns dark on standing also when alkalanised
- Cartilage & CT stained grey
- Calcified cartilage
- Early OA 2° brittleness
- Especially affects Spine
- difficult to differentiate from ankylosing spondylitis
- dense calcification of discs with narrowing of intervertebral space
- Brownish-black pigment in connective tissue
Presentation
- Presents 4th decade
- Generalised degenerative disease is often presenting complaint
- back pain then knees / shoulders / hips
- Sweat stains clothes
- Dark Urine
