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It is possible that the main title of the report Alkaptonuria is not the name you expected.

Disorder Subdivisions

  • None

General Discussion

Alkaptonuria is a rare genetic metabolic disorder characterized by the accumulation of homogentisic acid in the body. Affected individuals lack enough functional levels of an enzyme required to breakdown homogentisic acid. Affected individuals may have dark urine or urine that turns black when exposed to air. However, this change may not occur for several hours after urination and often goes unnoticed. Aside from dark urine that is present from infancy, affected individuals generally do not develop symptoms (asymptomatic) during infancy or childhood and often remain unaware of their condition until adulthood. Affected individuals eventually develop ochronosis, which is the bluish-black discoloration of connective and other tissue within the body. Affected individuals may develop discoloration of the skin overlying cartilage within the body such as over part of the outer ear. In some cases, the whites of the eyes (sclera) may also become discolored. In adulthood, affected individuals also develop progressive arthritis of the spine and large joints. The HDG gene codes for the enzyme required for the breakdown of homogentisic acid. Mutations in HDG cause alkaptonuria.

Supporting Organizations

AKU Society of North America

10451 Roselle Street #300
San Diego, CA 92121
Tel: (800)549-8110

Alkaptonuria Society

66 Devonshire Road
Cambridge, CB1 2BL
United Kingdom
Tel: +44 (0)1223 322897

CLIMB (Children Living with Inherited Metabolic Diseases)

Climb Building
176 Nantwich Road
Crewe, CW2 6BG
United Kingdom
Tel: 4408452412173
Fax: 4408452412174

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311

NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

Information Clearinghouse
One AMS Circle
Bethesda, MD 20892-3675
Tel: (301)495-4484
Fax: (301)718-6366
Tel: (877)226-4267

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). For a full-text version of this report, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report.

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

Last Updated:  7/1/2015
Copyright  2014 National Organization for Rare Disorders, Inc.