Black acid

Introduction Black aciduria (alcaptonuria) is an autosomal recessive disorder, one of the earliest inborn metabolic abnormalities proposed by Garrod in 1908. The disease is a deficiency of congenital uric acid oxidase, so the uric acid which is decomposed by tyrosine cannot be further decomposed into acetoacetic acid. Excessive uric acid is excreted in the urine and oxidized to black in the air. The uric acid is oxidized in the air to a dark brown enamel-type substance. In vivo, P-diphenol oxidase converts uric acid into a poly-anthraquinone pigment.

Cause

The disease is a deficiency of congenital uric acid oxidase, so the uric acid which is decomposed by tyrosine cannot be further decomposed into acetoacetic acid. Excessive uric acid is excreted in the urine and oxidized to black in the air.

an examination

Related inspection

Urine routine urethral secretion examination

There is a large amount of uric acid in the urine of the disease, and the uric acid in the blood is not high. When the urine is exposed to the air, it turns black. When the urine is added, the color is darker. When the urine is strongly acidic, it does not easily turn black. The urine and ferric chloride of the child showed a deep purple reaction, and the urine reducing substance test (Bacillus test solution) was dark brown; the urine was added with saturated silver nitrate and the solution (dissolved with ammonia) turned black. The above screening method can be confirmed by chromatography, spectrophotometry, or measurement of urinary acid oxidase activity.

Differential diagnosis

(1) Phenol poisoning: Hydroquinone which is formed by the phenol entering the human body under the action of oxygen can be stained with black urine.

(2) The urine is black: there is a large amount of free oxygen, hemoglobin and oxyhemoglobin in the plasma, and the urine is dark red or black as the urine is discharged.

(3) dark urine: black urine, also known as dark brown urine, is more common in melanoma patients. Melanoma produces too much melanin. In the liver, small melanin is reduced to melanin. If a large amount of melanin is excreted from the urine and becomes melanin after oxidation, the urine of the melanoma patient becomes black urine as long as it is left for a while.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.