Ochronosis Presenting as Methemoglobinemia

Area of Science:

• Biochemistry
• Pathology
• Nephrology

Background:

• Ochronosis is characterized by blue-gray discoloration of collagenous tissues due to homogentisic acid (HGA) deposition.
• HGA accumulation, often linked to alkaptonuria or enzyme inhibition, can occur in renal disease.
• Methemoglobinemia is a potential complication of HGA accumulation in patients with kidney dysfunction.

Observation:

• A 60-year-old woman with renal disease and anemia presented with progressive gray skin discoloration and weakness.
• Laboratory findings revealed significant methemoglobinemia (24.5%) and anemia (hemoglobin 8.1 g/dL).
• Despite intensive medical interventions, including methylene blue, exchange transfusion, and renal replacement therapy, the patient's condition deteriorated.

Findings:

• Autopsy confirmed ochronosis, with characteristic pigment found in ribs and cartilage.
• The patient was diagnosed with ochronosis secondary to alkaptonuria, complicated by methemoglobinemia.
• The clinical course and autopsy findings strongly suggested a link between progressive renal dysfunction, alkaptonuria, and fatal methemoglobinemia.

Implications:

• This case underscores the importance of considering alkaptonuria in patients with unexplained blue-gray skin discoloration and renal failure.
• Methemoglobinemia in the context of chronic skin changes and kidney disease warrants prompt investigation for underlying alkaptonuria.
• Early recognition and management of alkaptonuria may be crucial in preventing severe complications like methemoglobinemia.