Alcaptonuria, also called ochronosis, is a rare disease that is caused by an error in the metabolism of amino acid phenylalanine and tyrosine as a result of small mutation of DNA. This disease is due to the lack of enzyme dioxygenase of homogentisate or homogentisate oxygenate. This will lead to the accumulation of homogentisic acid, which is the intermediate compound formed from the metabolism of these amino acids. Under normal conditions, it cannot be detected in the blood.
Alcaptonuria does not have a cure, however, the treatment administered helps in reducing the symptoms and it is recommended to follow a diet that is low in foods that contain phenylalanine and tyrosine. The increased consumption of foods rich in vitamin C is recommended to control the condition.
Symptoms of alcaptonuria
Symptoms of alcaptonuria begin to appear as early as in childhood and it is characterized by a darker urine and the appearance of spots on the skin and ears. However, some people may become asymptomatic and the symptoms will only show from the age of 40. This will in turn make treatment more difficult as the symptoms are more severe.
In general, the symptoms of alcaptonuria are:
- Dark urine, that is almost black
- Bluish ear wax
- Black spots on the whites of the eye, around the ear and larynx
- Arthritis that causes joint pain and limitation of movements
- Cartilage stiffness
- Kidney and prostate stone, in the case of men
- Heart problems
The dark pigment accumulates in the skin majorly in the armpits and groin and when perspiring it can pass on to clothing. The patient will have difficulty breathing due to the stiffness of the costal cartilage and hoarseness due to the stiffness of the hyaline membrane. In the advanced stages, the acid can accumulate in the veins and arteries of the heart which can result in serious heart problems.
The diagnosis of alcaptonuria is done through analysis of the symptoms which are mainly dark spots that are evident on various parts of the body. Laboratory tests may also be carried out to detect the concentration of the homogentisic acid in the blood or detect the mutation using molecular tests.
How treatment is done
Treatment for alcaptonuria is done to relive the symptoms since it is a genetic disorder of the recessive character. Therefore, it may be recommended to use analgesics or anti-inflammatory drugs to relive joint pain and cartilage stiffness. Therapy sessions can also be done using corticosteroid infiltration so as to improve the mobility of the affected joints.
Moreover, it is also ideal to consume a diet that is low in phenylalanine and tyrosine since these are the precursors of homogentisic acid. For this reason, one should avoid consuming cashew nuts, almonds, brazil nuts, avocado, mushrooms, egg white, banana, milk and beans.
Consumption of foods rich in vitamin C or ascorbic acid is also recommended as a form of treatment as it is effective in reducing accumulation of brown pigments in the cartilage and development of arthritis.