Alkaptonuria: Why does it turn urine black? Urologist explains the long-term effects | Health
Apr 03, 2025 08:49 PM IST
Alkaptonuria is a rare genetic disorder that can lead to joint diseases and kidney stones.
Alkaptonuria is a rare genetic disorder caused by a deficiency of the enzyme homogentisate 1,2-dioxygenase. In an interview with HT Lifestyle, Dr Abhishek Agrawal, Consultant urologist, Jupiter Hospital Thane explained why t turns urine black, “This enzyme is essential for breaking down homogentisic acid, a byproduct of amino acid metabolism. When the enzyme is deficient, homogentisic acid accumulates in the body and is excreted in the urine. Upon exposure to air, this acid oxidizes, causing the urine to turn dark brown or black—a hallmark symptom of alkaptonuria.” Also read | World Kidney Day 2025: What your urine can reveal about your kidney health? Doctor explains
Early signs of alkaptonuria:
“The black discoloration of urine is often the earliest and most noticeable sign of the disease, typically appearing in infancy or early childhood. However, many individuals with alkaptonuria may not experience other symptoms until later in life. The buildup of homogentisic acid over decades leads to a condition called ochronosis, where the acid binds to connective tissues, turning them dark and causing gradual tissue damage,” Dr Abhishek Agrawal explained.
Long-term effects of alkaptonuria:
- Joint disease: One of the most significant long-term effects of alkaptonuria is degenerative joint disease. Homogentisic acid deposits in the cartilage cause the joints to become brittle and prone to wear and tear. Patients often develop severe arthritis, particularly in the spine, hips, and knees, by their 30s or 40s. This joint damage can lead to chronic pain, reduced mobility, and a diminished quality of life. Also read | Blood in urine: When to worry and what diagnostic steps to take
- Kidney and prostate stones: The buildup of homogentisic acid can crystallise in kidneys and prostate leading to stone formation.
- Pigmentation: Patients may also experience dark pigmentation in the ears, skin, and sclera (the white part of the eye), which is a visible sign of the disease’s progression.
Diagnosis and treatment of alkaptonuria:
“While there is currently no cure for alkaptonuria, early diagnosis and symptom management can improve patient outcomes. Treatment typically focuses on relieving pain, preserving joint function, and monitoring cardiovascular and renal complications,” the urologist explained. Also read | UTI on the rise among men: Doctor blames lifestyle and stress for this disturbing trend
Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.
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