[Black knee-ochronotic alterations in alkaptonuria]

Area of Science:

• Metabolic disorders
• Connective tissue diseases
• Genetics

Background:

• Alkaptonuria is a rare autosomal recessive metabolic disorder.
• It is caused by a deficiency in the enzyme homogentisate 1,2-dioxygenase.
• This deficiency leads to the accumulation of homogentisic acid.

Observation:

• A 53-year-old male patient presented with suspected knee joint empyema.
• Knee arthroscopy revealed ochronosis, characterized by bluish-black deposits.
• Histopathological biopsy confirmed the diagnosis of ochronosis.

Findings:

• Ochronosis is associated with alkaptonuria due to homogentisic acid accumulation.
• Homogentisic acid, a tyrosine degradation product, deposits in various tissues.
• Clinical manifestations include discoloration of connective tissues, sclera, and ear cartilage, as well as black urine.

Implications:

• Early diagnosis of ochronosis is crucial for managing associated complications.
• Understanding the genetic basis of alkaptonuria aids in diagnosis and potential therapeutic strategies.
• This case underscores the importance of considering rare metabolic disorders in joint pathology evaluations.