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Alkaptonuria

Related Terms

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Background

  • Alkaptonuria, also called black urine disease, is a rare inherited metabolic disorder characterized by dark brown or black urine and arthritis in adulthood. Arthritis is a condition in which inflammation and swelling in the joints cause pain.
  • Alkaptonuria is caused by a defect, or mutation, in the HGD gene. This gene provides instructions for making an enzyme called homogentisic acid oxidase (HGAO). Normally, HGAO helps break down the amino acids phenylalanine and tyrosine, which are important building blocks of proteins. Patients with alkaptonuria do not have enough HGAO. As a result, a substance called homogentisic acid, which is produced when phenylalanine and tyrosine are improperly broken down, accumulates in the body.
  • Excess homogentisic acid accumulates in the blood and is deposited in connective tissues, such as those found in and around joints. By age 40, patients develop ochronosis, a blue-black discoloration of connective tissue, including bone, cartilage, and skin, caused by deposits of ochre-colored pigment. Over time, a buildup of this substance causes cartilage and heart valves to become brittle and weakened. Buildup of homogentisic acid in the joints leads to arthritis.
  • Homogentisic acid is also excreted in urine, making the urine turn dark when exposed to air. Dark staining of the diapers sometimes can indicate alkaptonuria in infants, but most patients are not aware they have the disease until they are 30 to 40 years of age. Males tend to have an earlier onset of arthritic symptoms with a greater degree of severity than females, although the reason for this difference is unclear. Alkaptonuria is not life-threatening. Patients typically require lifelong treatment to manage symptoms, but they are expected to live relatively normal, healthy lives. Treatment may include dietary modifications and anti-inflammatory medications.
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Risk Factors

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Causes

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Signs and Symptoms

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Diagnosis

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Complications

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Treatment

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Integrative Therapies

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Prevention

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.