Alcaptonuria, also called ochronosis, is a rare disease characterized by an error in the metabolism of the amino acids phenylalanine and tyrosine, due to a small mutation in the DNA. This disease happens due to the lack of an enzyme, the homogentisate dioxigenase or homogentisate oxygenase, which leads to the accumulation of homogentisic acid, which is an intermediate compound in the metabolism of these amino acids and that under normal conditions is not detectable in the blood.
The disease manifests itself in childhood by changing the color of the urine, which turns black, in addition to the presence of dark spots on the skin and ears, for example. Some people, however, only become symptomatic after the age of 40, which makes treatment more difficult and the symptoms are usually more severe.
Alcaptonuria has no cure, however the treatment helps to reduce symptoms, and it is recommended to follow a diet low in foods containing phenylalanine and tyrosine, in addition to increasing consumption of foods rich in vitamin C, such as lemon, for example.
Symptoms of Alkaptonuria
The most characteristic symptoms of alkaptonuria are:
- Dark, almost black urine - Know other causes of black urine; Bluish earwax; Black spots on the white part of the eye, around the ear and larynx; Deafness; Arthritis that causes joint pain and limited movement; Cartilage stiffness; Kidney and prostate stones for men; Heart problems.
The dark pigment can accumulate on the skin in the regions of the armpit and groin that, when perspiring, can pass to the clothes. It is common for a person to have difficulty breathing due to the process of stiff costal cartilage and hoarseness due to the stiffness of the hyaline membrane. In the late stages of the disease, acid can accumulate in the veins and arteries of the heart, which can lead to serious heart problems.
The diagnosis of Alkaptonuria is made by analyzing the symptoms, mainly by the dark coloration characteristic of the disease that appears in various parts of the body, in addition to laboratory tests that aim to detect the concentration of homogentisic acid in the blood, mainly, or to detect the mutation through molecular examinations. Understand what molecular diagnosis is and what it is for.
How the treatment is done
The treatment for alkaptonuria aims to relieve symptoms, since it is a recessive genetic disease. Thus, the use of analgesics or anti-inflammatory drugs may be recommended to relieve joint pain and cartilage stiffness, in addition to physiotherapy sessions, which can be done with corticosteroid infiltration, to improve the mobility of the affected joints.
In addition, it is recommended to follow a diet low in phenylalanine and tyrosine, since they are precursors of homogentisic acid, so it is recommended to avoid the consumption of cashews, almonds, Brazil nuts, avocados, mushrooms, egg white, banana, milk and beans, for example. See which foods are high in phenylalanine and tyrosine that should be avoided.
Intake of vitamin C, or ascorbic acid, is also suggested as a treatment, since it is effective in reducing the accumulation of brown pigments in cartilage and developing arthritis. Learn more about ascorbic acid.
