Ochronosis

Ochronosis is a disease characterized by the accumulation of homogentisic acid. It is subclassified as endogenous and exogenous.

The endogenous form is genetic and autosomal recessive. Alcaptonuria is a specific genetic defect that causes ochronosis.

Gross

• Tissue with blue-grey discolourization.
  • Affected tissues: articular and auricular cartilage, tendons, ligaments heart valves, sclera, cornea.
• Dark urine (after exposure to sunlight).

Images:

• Ochronosis - eye (nejm.org).
• Ochronosis - hip (nih.gov/CMAJ).

Microscopic

Features - cartilage:

• Deposits of (acellular) brown pigment (H&E sections) - key feature.

Image:

• Ochronosis (rsna.org).