Rare Rheumatology News

Disease Profile


Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable



Ochronosis is the bluish-black or grey-blue discoloration of the skin, especially the ear cartilage, the ocular (eye) tissue, and other body locations. It can occurs in individuals with alkaptonuria, an inherited metabolic disorder; or because of exposure to various substances. Ochronosis typically occurs in adults, but has been reported in children. Ochronosis associated with alkaptonuria is caused by a mutation in the HGD gene, which results in the accumulation and deposition of homogentisic acid (HGA) in cartilage.[1] The affected tissue becomes weak and brittle with time, leading to chronic inflammation, joint pain, and osteoarthritis. Alkaptonuria is inherited in an autosomal recessive manner. Alkaptonuria can be diagnosed based on the symptoms, laboratory testing, and genetic testing. There is no specific treatment for ochronosis associated with alkaptonuria and treatment is based on the symptoms.[1] 

When ochronosis is due to exposure to substances (called exogenous ochronosis), the condition is not inherited.[2][3] Exogenous ochronosis is associated with malarial drugs, skin-lightening creams and over-exposure to the sun. Other than the skin findings, there are no other health affects. Exogenous ochronosis is difficult to diagnose. There is no specific treatment for this condition. Several different treatment options are available including prescription skin creams, vitamins, and laser treatments.[2]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

    • DermNet NZ is an online resource about skin diseases developed by the New Zealand Dermatological Society Incorporated. DermNet NZ provides information about this condition.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.


        1. Alkaptonuria. National Organization for Rare Disorders (NORD). Updated 2017; https://rarediseases.org/rare-diseases/alkaptonuria/.
        2. Vashi N. Kundu R. Acquired hyperpigmentation disorders. UpToDate. Sept 28, 2017; https://www.uptodate.com/contents/acquired-hyperpigmentation-disorders.
        3. Bhattar PA, Zawar VP, Godse KV, Patil SP, Nakarni NJ, Gautam MM. Exogenous Ochronosis. Indian J Derm. Nov-Dec 2015; 60(6):537-43. https://www.ncbi.nlm.nih.gov/pubmed/26677264.