Alkaptonuria is also called black urine disease.
Alkaptonuria is a genetic metabolic disorder in which body cells cannot break down two amino acids called tyrosine and phenylalanine.
This metabolic disorder results in the collection of homogentisic acid in the body.
Due to the presence of excess homogentisic acid, urine and other parts of the body turn dark coloured and it leads to a range of problems over time.
According to the NIH – National Institutes of Health, this genetic metabolic disorder affects about one in every hundred thousand people worldwide and is more common in the Dominican Republic and Slovakia, affecting about one in twenty thousand people. It affects both males and females in equal numbers. Among children, only 20 to 21% of the children under the age of 1 year having the disease are identified.
Explore more: Genetic Disorders
Causes of Alkaptonuria
Alkaptonuria is a rare inherited disorder caused by a mutation in the homogentisate 1,2-dioxygenase (HGD) gene.
It is an autosomal recessive condition, which implies that both the parents must have the gene to pass the disease on to their infants.
Also Refer: Chromosomal Abnormalities in Humans
Diagnosis of Alkaptonuria
Alkaptonuria can be diagnosed based upon the characteristic symptoms, patient’s history, and other specialised test reports.
Alkaptonuria can be diagnosed in people with osteoarthritis, especially those with early symptoms. Alkaptonuria should be suspected in individuals with dark urine. But some individuals with alkaptonuria do not have dark urine. Hence, it may be advisable to rule out the disorder for all individuals.
There are a variety of specialised tests used for the identification of alkaptonuria, which includes:
- Elevated levels of homogentisic acid in the urine by chromatography
- Echocardiography to detect cardiac complications
- Molecular genetic testing
Symptoms of Alkaptonuria
Alkaptonuria is an inherited condition that does not develop symptoms until about 30 years. They are due to the chronic assemblage of homogentisic acid within the connective tissue, mainly the cartilage.
The dark stains on a baby’s diaper are among the earliest signs of alkaptonuria and are present from birth. There are few other symptoms during childhood, which become more evident with age.
Other symptoms of alkaptonuria include:
- Arthritis
- Black earwax
- Prostate and kidney stones
- Signs of early-onset osteoarthritis
- Dark spots in the sclera of the eyes
- Dark-coloured sweat or sweat stains
- Thickened and darkened cartilage in the ears
- Chronic stiffness or pain in your lower back or large joints
- Blue speckled discolouration of the skin, particularly around sweat glands
- Shortness of breath or difficulty in breathing is caused due to the stiffness of bones and muscles around the lungs, and it prevents the chest from expanding.
In severe cases, alkaptonuria can also lead to heart problems caused by the buildup of homogentisic acid that leads to the hardening of the heart valves.
Explore more: Symptoms of Various Diseases
Available Treatment for Alkaptonuria
Alkaptonuria is an autosomal recessive condition, which means it is a lifelong condition; hence currently, there is no specific treatment or cure for alkaptonuria.
However, other treatments can be mainly focused on managing symptoms and preventing or reducing possible complications, such as:
- Arthritis
- Heart disease
- Prostate and kidney stones
Anti-inflammatory medications can be used for joint pain. Along with these medications, specific physical and occupational therapies may help maintain strength and flexibility in the muscles and joints.
Other possible treatments for these symptoms include:
- Shoulder, knee, or hip replacement.
- Surgery to replace aortic or mitral heart valves.
In severe cases, heart valve replacement may be necessary. Other therapies to treat chronic kidney or prostate stones.
This concludes an introduction to alkaptonuria.
Stay tuned to BYJU’S for more information related to alkaptonuria, causes, available treatments, symptoms and other related topics.
Frequently Asked Questions
What is Alkaptonuria?
Alkaptonuria is a rare inherited disorder that occurs when our body cannot produce enough enzymes to break down a toxic substance called homogentisic acid.
Which enzymes are involved in the breakdown of homogentisic acid?
Homogentisate 1,2-dioxygenase is an enzyme that breaks down the amino acids tyrosine and phenylalanine.
Who is more prone to alkaptonuria – male or female?
Alkaptonuria is an inherited autosomal recessive trait caused by the lack of renal and hepatic homogentisic acid oxidase. It affects both males and females in equal numbers.
What is the leading cause of alkaptonuria?
Alkaptonuria is a recessive abnormality caused by the homogentisate acid oxidase enzyme deficiency.
What are the symptoms of alkaptonuria?
Dark or black coloured urine is one of the earliest symptoms of alkaptonuria. The signs and symptoms of alkaptonuria usually do not develop until approximately 30 years of age.
Symptoms of Alkaptonuria include:
- Kidney stones and prostate stones
- Dark-coloured sweat or sweat stains
- Signs of early-onset osteoarthritis
- Thickened and darkened cartilage in your ears
- Stiffness or pain in your lower back or large joints
How is alkaptonuria treated?
Currently, there is no specific treatment or cure for alkaptonuria. However, other therapies mainly focus on managing symptoms and preventing or reducing possible complications.
Can alkaptonuria be managed?
Yes. Alkaptonuria can be managed.
Alkaptonuria is a lifelong condition. As we all know, there is currently no specific treatment or cure. However, a few medicines, painkillers, and lifestyle changes can help patients cope with their symptoms.
Specific lifestyle changes can also manage alkaptonuria, such as:
- A low-protein diet
- Emotional support
- Regular gentle exercise for relieving stress, building muscle and strengthening the joints.
Are there any other names for this inherited disorder?
Yes.
Alkaptonuria is also called by other names:
- AKU
- Alcaptonuria
- Homogentisic acidura
- Homogentisic acid oxidase deficiency.
Why is alkaptonuria also called black urine disease?
Alkaptonuria is also called black urine disease because an individual with this disorder lacks the enzyme necessary for the catabolism of homogentisic acid (HGA). Therefore, an excess amount of homogentisic acid is excreted in the urine and deposited in connective tissues throughout the body, especially the cartilage leading to a dark colour. The urine is dark and becomes black on standing.
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