KnowraRare diseaseRare diseaseA disease affecting a small proportion of a population. Its formal prevalence threshold varies by jurisdiction.BriefConnectDiagnostic odyssey: A prolonged search for the correct diagnosis, often involving multiple clinicians and tests. Uncommon symptoms and limited clinical familiarity can lengthen the path to diagnosis.Genetic disorder: A disease caused by changes in DNA or by abnormalities in chromosome structure or number. Many rare diseases result from inherited or newly arising genetic changes.Disease prevalence: The proportion of a population that has a disease at a specified time or over a period. Rare-disease thresholds are defined using prevalence, though jurisdictions choose different cutoffs.Whole-exome sequencing: A sequencing method that reads most protein-coding regions of the genome. It can identify disease-causing variants when standard testing fails.Orphan drug: A medicine developed or designated to treat a disease affecting a small patient population. Small markets can discourage development without targeted incentives.De novo mutation: A genetic change that first appears in an individual rather than being inherited from a parent. It can cause a rare disease without any family history.Orphanet: A European information portal and classification resource for rare diseases and orphan drugs. Its nomenclature helps standardize names and data across rare conditions.Whole-genome sequencing: A method that determines nearly all of an individual’s DNA sequence. It can detect rare-disease variants outside protein-coding regions.Orphan Drug Act: A 1983 United States law offering incentives to develop treatments for rare diseases. It established a major model for addressing weak commercial incentives.Mendelian inheritance: Patterns of inheritance in which traits are transmitted through single genes according to Mendel’s principles. These patterns help explain recurrence risks in many single-gene rare diseases.Show all 23Linked from 15 pagesCongenital disorderRelated: Many congenital disorders are rare, creating challenges for diagnosis and specialized care.AlkaptonuriaNarrower topic: Its rarity can make recognition and access to specialist care more difficult.Neglected tropical diseasesCompared with: Rarity describes frequency, whereas neglect describes patterns of attention and resource allocation.Case reportRelated: Individual reports can describe its presentation and course in clinical detail.ProgeriaNarrower topic: Small patient populations make clinical trials and long-term outcome studies especially difficult.Chronic conditionCompared with: Rarity concerns how many people are affected, not how long a condition lasts.Birth defectRelated: Many rare diseases include congenital abnormalities and require specialized care.Pentasomy XNarrower topic: Pentasomy X is rare enough that large, representative clinical studies are difficult.Show all 15