What is alkaptonuria? Symptoms, Diagnosis and Treatment of Alkaptonuria.

What is Alkaptonuria?

Alkaptonuria is a rare genetic disorder that affects the metabolism of amino acids – phenylalanine and tyrosine.

Due to this, it leads to the buildup of a pigment called homogentisic acid in the body. Accumulation of homogentisic acid can cause joint and spine problems and the discoloration of urine to a dark color. It is where the disease gets its name from.

Known till date, there is no cure for alkaptonuria. However, a low tyrosine and phenylalanine diet can help reduce the symptoms.

What are the symptoms of alkaptonuria?

Since alkaptonuria is a rare genetic disorder, the symptoms of alkaptonuria vary in severity and onset. However, most of them includes the following.

Alkaptonuria urine vs normal urine
Alkaptonuria urine comparison | Source: Sciencedirect
  1. Dark coloration of urine: This is the earliest symptoms of alkaptonuria. It is caused due to the buildup of homogentisic acid in urine.
  2. Joints and spinal problems: The prolonged accumulation of homogentisic acid in the body can result in joint and spine problems – such as osteoarthritis, spinal stenosis, etc.
  3. Cardiovascular disease: Rarely, people with with alkaptonuria may also develop heart valve problems (aortic aneurysms).
  4. Problems in the eye: This is rare but a serious complication. Alkaptonuria might result in development of a corneal pigmentation called the ochronosis.
  5. Kidney stones: Some people with alkaptonuria are at risk of developing kidney stones.

A significant things is that the symptoms of alkaptunoria might vary greatly between individuals. In some cases- there might not even be any symptoms at all.

Diagnosis of Alkaptonuria

Alkaptonuria testing is done by blood, urine or genetic methods. Sometimes the alkaptonuria testing requires a combination of tests as well as detailed medical history. Generally, a genetic counselor provides the information on the condition of the disease and the interpretation of the alkaptonuria tests.

  1. Urine test: A urine sample is tested for detecting the level of homogentisic acid.
  2. Blood test: Blood sample is analyzed to determine the levels of tyrosine and phenylalanine.
  3. Genetic test: A genetic test is performed to detect mutations in the HGD gene. This gene is responsible for producing the enzyme homogentisate 1,2-dioxygenase (HGO), required for the breakdown of homogentisic acid.

Alkaptonuria Treatment

Clinically, there is no cure for alkaptonuria.

However, there are some treatment options can best help to manage the symptoms of the disease and reduce the buildup of homogentisic acid in the body.

The alkaptonuria treatment options include:

  1. A low tyrosine and phenylalanine diet can help reduce the symptoms and slow down the progression of the disease.
  2. To manage the pain of spine and joints, some over-the-counter or prescription pain medications can be used.
  3. In severe cases, surgery might be necessary to mitigate joint or spine problems.
  4. Studies have shown some antioxidants like N-acetylcysteine have shown a protective effect on joints and helped reduce the formation of homogentisic acid in the body.

Meanwhile, it is important to work closely with doctors or genetic counselor to come up with a personalized treatment plan for alkaptonuria.

Regular monitoring and management of the condition can help to improve quality of life and complications.

More About Alkaptonuria

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