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Definition

What is alkaptonuria?

Alkaptonuria is a rare inherited condition that occurs when your body is not able to produce enough of an enzyme called homogentisic dioxygenase (HGD), which is used to break down a toxic substance called homogentisic acid. As a result, when your body can’t produce enough HGD, homogentisic acid builds up in your body.

The increasing of homogentisic acid certainly causes your bones and cartilage to become discolored and brittle. This typically leads to osteoarthritis, especially in your spine and large joints.

Patients with alkaptonuria also have urine that turns dark brown or black when it’s exposed to air.

How common is alkaptonuria?

Alkaptonuria is actually a rare disease. According to the National Organization of Rare Disorders (NORD), the exact number of cases is unknown. It is estimated to occur in 1 of every 250,000. However, it is more common in certain areas of Slovakia, Germany, and the Dominican Republic.

However, it can be managed by reducing your risk factors. Please discuss with your doctor for further information.

Symptoms

What are the symptoms of alkaptonuria?

The common symptoms of alkaptonuria are:

  • Dark spots in the sclera (white) of your eyes
  • Thickened and darkened cartilage in your ears
  • Blue speckled discoloration of your skin, particularly around sweat glands
  • Dark-colored sweat or sweat stains
  • Black earwax
  • Kidney stones and prostate stones
  • Arthritis (especially hip and knee joints)

 

Signs and symptoms of alkaptonuria become clearer when you grow up. Most noticeably, your urine may turn dark brown or black when it’s exposed to air. By the time you reach your 20s or 30s, you may notice signs of early-onset osteoarthritis.

Alkaptonuria can sometimes lead to heart problems. The buildup of homogentisic acid causes your heart valves to harden. This can keep them from closing properly, resulting in aortic and mitral valve disorders.

When should I see my doctor?

If you have any questions, please consulting with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.

Causes

What causes alkaptonuria?

Alkaptonuria is caused by a mutation on your homogentisate 1,2-dioxygenase (HGD) gene. It is an autosomally recessive condition. This means that both of your parents must have the gene in order to pass the condition on to you.

Risk factors

What increases my risk for alkaptonuria?

There are many risk factors for alkaptonuria, such as:

  • Because alkaptonuria is inherited, the only known risk factor is a family history of the disorder. Men and women are affected in equal numbers. The prevalence is estimated to be about one in 250,000 people worldwide. It is difficult to estimate the number of cases of alkaptonuria because newborn screening for alkaptonuria is not widely practiced and some people that have a mutation that causes the disorder do not show symptoms.
  • Although a rare disorder, the frequency of alkaptonuria is higher in certain populations. It is more popular in certain areas of Slovakia where it affects approximately one in 19,000 people. It is also more common in the Dominican Republic, but the prevalence there is not known.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is alkaptonuria diagnosed?

If your doctor suspects that you experience alkaptonuria, he/she will perform an exam thoroughly to determine this condition.

In case, your doctor may suspect you have alkaptonuria because of your dark brown urine when it’s exposed to air. They may also test you for the condition if you develop early onset osteoarthritis.

Your doctor can use a test called gas chromatography to look for traces of homogentisic acid in your urine. They can also use DNA testing to check for the mutated HGD gene.

Family history is very useful in making a diagnosis of alkaptonuria. However, many people don’t know they carry the gene. Your parents might be carriers without realizing it.

How is alkaptonuria treated?

There is actually no specific treatment for alkaptonuria.

You should be put on a low-protein diet. Your doctor may recommend large doses of ascorbic acid, or vitamin C, to slow down the accumulation of homogentisic acid in your cartilage. However, NORD warns that long-term use of vitamin C has generally proven ineffective for treating this condition.

Other treatments for alkaptonuria are focused on preventing and relieving possible complications, such as:

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage alkaptonuria ?

The following lifestyles and home remedies might help you cope with:

  • Observation of dark colored urine in infants or young children should be promptly evaluated
  • Genetic counseling for known cases and those with a family history can help.
  • Prenatal tests to detect the condition in the womb may be considered.

For people who have already diagnosed alkaptonuria, they should follow medical advice and regular monitoring can help in early detection and treatment of symptoms.

Some of the feasible complications include arthritis, heart diseases and kidney or prostate stones, mainly caused by deposition of the excess acid. Following a healthy routine with a balanced meal and restricting high protein intake can help. Regular exercise may be carried out with medical advice.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Review Date: August 3, 2017 | Last Modified: August 3, 2017

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