The National Library of Medicine's Unified Medical Language System (UMLS) is used to classify and organize diseases and disease categories.

• Reference: UMLS Vocabulary Standards and Mappings Downloads

Data from Orphanet  and Human Phenotype Ontology (HPO)  are used to provide information on a disease's symptoms, genes, inheritance, population estimates, and more.

• Reference: Access aggregated data from Orphanet at Orphadata . Orphanet is an online database of rare diseases and orphan drugs. Copyright, INSERM 1997.
• Reference: Download data from HPO . Kohler S, Gargano M, Matentzoglu N, et al., The Human Phenotype Ontology in 2021 , Nucleic Acids Research, Volume 49, Issue D1, 8 January 2021, Pages D1207–D1217. 

Data from the National Center for Biotechnology Information's MedGen is used to provide genetic testing information available for a disease.

• Reference: MedGen Data Downloads and FTP

Data from the National Library of Medicine's Newborn Screening Coding and Terminology Guide is used to note if a disease is included on Federal or State recommendations for newborn screening testing.

• Reference: Data from the Newborn Screening Coding and Terminology Guide is available here. Downs SM, van Dyck PC, Rinaldo P, et al. Improving newborn screening laboratory test ordering and result reporting using health information exchange . J Am Med Inform Assoc. 2010 Jan-Feb;17(1):13-8. 

Content References:

National Academies of Sciences, Engineering, and Medicine. 2015. Improving Diagnosis in Health Care . Washington, DC: The National Academies Press.  

U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion. (2015). Health Literacy Online: A Guide for Simplifying the User Experience.