Urine that Turns Black?
Clear urine turns black on standing?
Think Alkaptonuria — rare tyrosine metabolism disorder
Due to homogentisic acid buildup
Leads to ochronosis: dark cartilage, stiff joints
Clue: Black diapers in infants!
do you know more about it??
Urine That Turns Black?
Yes — classic clue for Alkaptonuria, a rare autosomal recessive disorder.
Cause:
Deficiency of homogentisate oxidase → buildup of homogentisic acid (HGA) in tissues and urine.
Key Signs:
Black urine on standing (oxidation of HGA)
Ochronosis: bluish-black pigmentation in connective tissues (ear cartilage, sclera)
Arthropathy: stiff spine, early-onset osteoarthritis, especially in large joints
Pigmented kidney/bladder stones
In infants: Black staining of diapers may be the earliest clue.
Diagnosis: Elevated HGA in urine
Management: No cure yet; low-protein diet (↓ phenylalanine & tyrosine), Vitamin C may slow pigment deposition, and nitisinone is under study.
Long-term: Watch for cardiac valve involvement and spinal issues.
Alkaptonuria
Black urine disease
It’s an Inborn error of Metabolism due to buildup of homogentisic acid oxidase
Yes! Alkaptonuria is an autosomal recessive disorder caused by deficiency of homogentisate oxidase, leading to homogentisic acid accumulation.
It darkens urine on standing and deposits pigment in connective tissues—a condition called ochronosis.
Long-term effects include early-onset arthritis, especially of the spine and large joints.