ALKAPTONURIA
Alkaptonuria (Black Urine Disease)
- It is due to deficiency of homogentisate oxidase.
- Inheritance- autosomal recessive disorder.
- It is a first inborn error detected
- It belongs to Gerrad’s Tetrad.
- Homogentisate accumulates in tissues and blood and is excreted into urine.
Biochemical Defect-
- Homogentisic acid is oxidised by polyphenol oxidase to benzoquinone acetate then polymerized to alkaptone bodies.
Clinical Features-
- Blackening of Urine.
- Alkapton deposition occurs in sclera, ear, nose, cheeks and intervertebral disc resulting in a condition called Ochronosis.
- Leading to pigmentation.
- Arthritis.
- *No mental retardation.
Diagnosis-
- Alkalanization increases darkening of urine.
- Benedict’s test is positive in urine.
- Ferric chloride test is positive.
- Silver nitrate is positive.
Treatment-
- Low phenylalanine diet
- Symptomatic treatment.
- New drug is Nitisinone.
Exam Important
- Belongs to Gerrads Terad ( Alkaptonuria, Albinism, Pentosuria, Cystinuria)
- No mental retardation is seen in alkaptonuria
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