An orphan or rare disease is generally considered to have a prevalence of fewer than 200,000 affected individuals in the United States. Certain diseases with more than 200,000 affected individuals are included, but subpopulations of these conditions may be less than the prevalence standard for rare disease. This list includes rare diseases and conditions for which information requests have been made to the ORD. It is updated on a regular basis. We welcome suggestions for additions to the list and your recommendations may be sent via email to: ord@od.nih.gov Note: The names of the conditions may not necessarily be the most common. Clicking on one of the names below will take you to a page that contains specific information for that disease. The links on these pages are a work in progress, so please check back often for new information. Enter the complete condition name or a few letters of the condition name for which you are looking. Your search will return either an exact match or a list of possible matches based on the text string you enter. Click on the condition name of interest for links to further resources. If your search retrieves no results, try browsing the list alphabetically.

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10q Partial trisomy

11-Beta-hydroxylase deficiency

17-Beta-hydroxysteroid dehydrogenase deficiency

18-Hydroxylase deficiency

18p syndrome

19r Chromosome syndrome

1p36.33 deletion

2-hydroxyethyl methacrylate sensitization

2-Hydroxyglutaricaciduria

2-Methylacetoacetyl CoA thiolase deficiency

3-@methylcrotonyl-coa carboxylase 1 deficiency

3-@methylcrotonyl-coa carboxylase 2 deficiency

3-@methylglutaconicaciduria, type 3

3-Hydroxyisobutyric aciduria

3C syndrome

3M syndrome

4-Alpha-hydroxyphenylpyruvate hydroxylase deficiency

4-Hydroxyphenylacetic Aciduria

46,XX Gonadal dysgenesis epibulbar dermoid

47,XXX syndrome

47,XYY syndrome

49,XXXXX syndrome

49,XXXXY syndrome

5-alpha-Oxoprolinase deficiency

5-Alpha-reductase 2 deficiency

5-Nucleotidase syndrome

5q- syndrome

6-@mercaptopurine sensitivity

6-Pyruvoyl-tetrahydropterin synthase, deficiency

7-Dehydrocholesterol reductase deficiency

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Last Reviewed: Monday, November 15, 2004