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Five Ways to Define and Redefine Rare Diseases

Thanks to years of research, advocacy efforts, and awareness campaigns, the spotlight shines more brightly than ever before on rare diseases. More than 7,000 have been identified, dating back to ancient times. They are a diverse group, seemingly defying categorization: widely recognized (hemophilia, Duchenne muscular dystrophy) or less well known (Fabry disease, Gaucher disease); affecting heart, blood, lungs, or bones; presenting at birth or first appearing in adulthood; impacting a single system in the body or multiple organs. While the threads that connect them can be challenging ones – frequent misdiagnosis, financial burdens, lack of approved drugs – remarkable advances in therapeutics, treatment, and care have occurred in the last decade. The following are five ways rare diseases continue to be defined and redefined, with the ultimate hope of evolving from ‘rare diseases’ to ‘treatable’ to ‘cured diseases.’

1) Defining rare diseases by prevalence is not an exact science because the numbers are categorized differently globally.

  • In the U.S., a rare disease is defined as one that affects less than 200,000 Americans.That category contains the “ultra-rare” disease group of conditions for which there is no single accepted definition currently.2
  • In the European Union, a rare disease is a condition with a prevalence of 5 in 10,000 people or fewer. Here, a disease is defined as “ultra-rare” if it affects one person per 50,000 people, or fewer than 20 patients per million of population.2
  • In Japan, a disease is considered rare if it affects less than 50,000 people in the country or has a prevalence of less than one in 2,500 people.3
  • However it is defined, the numbers account for more than 300 million patients with rare diseases worldwide. As summed up succinctly by Orphanet: “Rare diseases are rare, but rare disease patients are numerous.”4

2) Rare diseases are challenging to define by origin, as multiple causes and factors have been identified.

  • While 80% or more of rare diseases are genetic, they can result from a single gene, as in alpha-1 antitrypsin deficiency; multiple genes, as in Williams-Beuren syndrome; they can be inherited or result from a chance mutation. Different variants in the same gene may also cause other rare diseases, e.g., variants in the PIK3CA gene are associated with Klippel–Trenaunay syndrome, the megalencephaly–capillary malformation syndrome, several cancers, and malformation syndromes.5
  • Infections can also cause rare diseases; exposure to toxic substances, such as asbestos, cadmium, chromium, phosphine, or formaldehyde; nutritional deficiencies; injuries; adverse effects of treatment, and many others.6
  • The same disease can be inherited or acquired due to toxic exposure. For example, some forms of aplastic anemia, such as Fanconi anemia, can be inherited but are more often caused by toxic exposure (benzene, chloramphenicol), an infection (hepatitis, herpes virus), radiation or chemotherapy, or another disease (rheumatoid arthritis).7
  • The exact cause of some other rare diseases remains unknown. For example, although Gorham-Stout disease, an extremely rare bone disorder, was identified years ago, no environmental, immunological or genetic risk factors have been identified, and most cases occur randomly.8

3) Less than 10% of rare diseases have an FDA-approved treatment, but research is robust.9

  • A growing pipeline of new pharmaceuticals, including gene therapies, promises to change this statistic in the coming decade. In 2021, orphan drugs accounted for 52% of all novel drugs approved by the FDA; in 2020, 58%.
  • An added boost to research is increasing recognition that the genetic pathways of rare diseases can also be seen in more common diseases, shedding light on the entire disease process.10
  • As distinguished English physician Dr. William Harvey noted in 1657, “… There is no better way to advance the proper practice of medicine than to give our minds to the discovery of the usual law of nature, by careful investigation of cases of rarer forms of diseases.”

4) Rare diseases are difficult to diagnose.

  • Despite increased awareness of rare diseases, the average time needed to receive an accurate diagnosis for most patients is six years after the onset of symptoms.11

  • Patients frequently need to see multiple providers to obtain a diagnosis, which is often impacted by limited diagnostic tools, misdiagnoses, and related obstacles.12

5) The cost of treating and caring for patients with a rare disease is substantial.

  • Medications developed specifically to treat rare diseases can cost families tens or hundreds of thousands of dollars each year. Many rare conditions are diagnosed in childhood and continue to affect individuals for decades.7
  • Estimated costs for people with rare diseases are multiple times higher than costs for people without those diseases. Studies estimate that the U.S.’s total cost for rare diseases is $966 billion, including direct medical expenses (e.g., drugs, doctor visits) and other nonmedical and indirect costs (e.g., loss of income).13

Orsini Specialty Pharmacy provides comprehensive and compassionate care for patients with rare diseases and complex conditions. Our high-touch care model centers around experienced, therapy-specific teams who deliver personalized patient care. Learn more about Orsini’s essential services for rare and complex disease therapies and our dedicated support for physicians, manufacturers, payors, and patients.