Inborn errors of metabolism
An inherited metabolic disease. The body cannot fully break down some protein building blocks. Urine turns dark in the air, and joint pain begins over the years.
Not part of the panel of Türkiye's National Newborn Screening Programme (heel-prick test). Source
This page is translated from the Turkish original.
This disease is followed through the “Inborn errors of metabolism” group.
An enzyme made by the HGD gene does not work well. Because of this, some protein building blocks are not fully broken down. An in-between product, homogentisic acid, builds up in the body. This substance settles like a dark dye in cartilage, joints and skin. Over time it hardens and makes the tissue brittle.
Symptoms usually develop slowly and vary from person to person.
Urine that turns dark, or wear-and-tear arthritis at a young age, suggests the disease. The diagnosis is made by finding very high homogentisic acid in the urine. A genetic test examines the HGD gene. The joints and heart are followed with imaging.
For adults, there is a medicine treatment specific to the disease that is approved in Europe. This treatment reduces the making of the substance that builds up. Pain treatment and physiotherapy help protect the joints. Avoiding sports and heavy work that put a lot of strain on the joints is recommended. If needed, joint replacement, heart valve or stone surgery is done. The doctor who follows the disease decides which treatment is suitable.
The disease is passed on through recessive inheritance. The mother and father are usually healthy carriers. For a couple who are both carriers, the chance of having an affected child is 1 in 4 in each pregnancy. Diseases of this kind may be more common in marriages between relatives. Genetic counselling guides the family.
Source: MedlinePlus Genetics: Alkaptonuria · NORD: Alkaptonuria · EMA: Orfadin (EPAR) – alkaptonüri endikasyonu
These facts are taken from Orphanet and MedlinePlus records (last checked: October 7, 2026). Frequency values are approximate ranges.
Non-profit patient and family organizations in Türkiye working on this disease or disease group. Links are for information; Doktorclub is not affiliated with these organizations and does not endorse them.
We could not find a patient association specific to this disease.
For all rare diseases: Nadir Hastalıklar Federasyonu
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USANew treatments and approvals
The FDA approved nitisinone to reduce homogentisic acid in the urine of adults with alkaptonuria.
A clinical trial is a regulated study that tests whether a new treatment is safe and whether it works, in patients who volunteer. Most trials look for a certain age, genetic change and health condition. Taking part is voluntary.
ClinicalTrials.gov currently lists no active interventional studies for this disease. Last checked: October 7, 2026.
See all studies on ClinicalTrials.gov · Joining clinical trials
EUNew treatments and approvals
In Europe, leriglitazone, taken by mouth, was authorized for cerebral adrenoleukodystrophy.
USANew treatments and approvals
Through the accelerated pathway, the FDA has approved pariglasgene brecaparvovec for glycogen storage disease type Ia.
EuropeResearch and clinical trials
A total of 58 patients from 34 centers in seven European countries were followed.
These codes identify the disease in international classifications and databases. They can help when you talk with your doctor or look for reliable sources.
Orphanet code: ORPHA:56 · ICD-11 5C50.10
Codes checked against WHO ICD-11 and Orphanet on October 7, 2026.
This page provides general information and does not replace diagnosis or treatment. Talk to your doctor about symptoms, diagnosis and treatment.