How Black Bone Disease Affects the Body

Black Bone Disease: Genetic and Drug-Related Causes

Black bone disease refers to a group of conditions characterised by dark pigmentation in bones and urine. Disorders like alkaptonuria or drug-induced pigmentation can lead to these changes. Understanding their symptoms and available treatments is essential for raising awareness and ensuring timely diagnosis and care.

What is Medicine-Induced Black Bone Disease?

Medicine-induced black bone disease results in a distinct blue, green or black colouration of the bones. This is mainly caused by prolonged use of minocycline medicines. The drug interacts with melanin and can cause pigmentation of skin, bones and teeth.

However, it differs from alkaptonuria, as it is a side effect rather than a genetic condition.

How Do Doctors Treat Medicine-Induced Black Bone Disease?

Usually, there is no cure for medicine-induced black bone disease. Doctors often recommend stopping the use of minocycline and tetracycline. However, in most cases, the discolouration can stay.

It is not a life-threatening condition, as it does not affect bone health. The discolouration is benign and does not raise any alarms.
 

What is Alkaptonuria?

Alkaptonuria is an autosomally recessive condition that people inherit. This genetic disorder causes kidney stones, dark urine, arthritis and pigmentation. The condition is also known as black urine disease and is part of a group of conditions known as inborn errors of metabolism.

How is Your Body Affected by Alkaptonuria?

The condition disrupts your body's ability to break down amino acids. It leads to ochronosis, which is characterised by discoloured sweat and brown discolouration of the sclera (white part of your eye) and skin. While Alkaptonuria is not acutely infectious or cancerous, it is a serious, progressive disease that can lead to severe disability from joint destruction and life-threatening complications from heart valve and coronary artery disease.

What Causes Black Urine in Alkaptonuria?

Homogentisate 1,2-dioxygenase (HGD) gene mutation causes black urine and other discolourations. This gene contains instructions on how to break down phenylalanine and tyrosine (amino acids).

However, when it mutates, the HGD enzyme does not function properly, causing improper breakdown of phenylalanine and tyrosine. As a result, homogentisic acid starts to build up in your body.

When your body contains excess homogentisic acid, it produces ochronotic pigment, which gives your urine a dark colour when exposed to air.

What are the main symptoms of alkaptonuria?

One of the most obvious symptoms of alkaptonuria is dark stains on a baby’s diaper. Symptoms usually show up during your late 20s and early 30s. However, the hallmark sign—dark brown or black urine that appears after exposure to air—is present from infancy.  They are as follows:

• Chronic stiffness in your back
• Pain in large joints
• Black earwax
• Dark-coloured sweats
• Darkened cartilage in your ear
• Black or brown spots in your eyes
• Blue-tinted discolouration around sweat glands
• Arthritis
• Kidney stones
• Prostate stones
   

The condition can also lead to the narrowing of your heart valves. This can result in aortic and mitral valve disorders, and heart valve replacement may be necessary.

What are the treatment options for alkaptonuria?

Doctors address the symptoms of alkaptonuria when treating this condition. There is no cure for this condition, and care is lifelong. Some common treatment methods are as follows:

• Nitisinone: It can help to slow down the progression of alkaptonuria. Nitisinone reduces homogentisic acid levels in your body.
• Dietary Changes: Nitisinone can cause various side effects. To combat them, doctors recommend adopting a low-protein diet.
• Regular Exercise: The condition can be painful to deal with. Therefore, gentle exercises can help ease symptoms. Moreover, exercise will also make your body strong and strengthen joints. If you are unsure about which exercise to do, consult a physiotherapist.
• Surgery: Alkaptonuria can make your cartilage hard and brittle, causing breakage and joint damage. Moreover, it can severely damage your aortic valve. Doctors will recommend surgery to address these issues and let you live a better quality of life.
• Emotional Support: Dealing with a lifelong and inherited disease can be tough and may lead to depression and anxiety. Therefore, emotional support through therapy is essential to manage the psychological consequences of the disease.
   

What is the Difference Between Alkaptonuria and Medicine-Induced Black Bone Disease?

While both conditions are associated with giving a dark pigment to the bones, they differ significantly in terms of features and causes. Here is a proper breakdown of the differences:

Black bone disease can refer to both a medicine-induced condition and alkaptonuria. While one is just a side effect, the latter is a lifelong inherited disease disrupting daily functions. Treating symptoms of alkaptonuria helps provide you with a better quality of life. Identifying symptoms is necessary to get diagnosed as soon as possible.

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