Sickle cell disease is officially classified as a rare disease in the United States. Under the Orphan Drug Act, any condition affecting fewer than 200,000 people qualifies as rare, and sickle cell disease affects an estimated 100,000 Americans. That said, calling it “rare” can be misleading, because globally it is one of the most common inherited blood disorders, affecting nearly 8 million people worldwide.
Why It Qualifies as a Rare Disease
The FDA defines a rare disease as one that affects fewer than 200,000 people in the United States. With roughly 100,000 Americans living with sickle cell disease, it falls well under that cutoff. The European Union uses a different threshold, defining rare as fewer than 5 in 10,000 people, and sickle cell disease meets that definition in Europe as well.
This classification matters because it opens the door to special incentives for drug development. The Orphan Drug Act gives pharmaceutical companies tax credits, extended market exclusivity, and other benefits when they develop treatments for rare diseases. Sickle cell disease’s rare designation played a role in the FDA’s 2023 approval of the first two gene therapies for the condition, both available to patients 12 and older with severe symptoms.
A Global Perspective Tells a Different Story
While the numbers are small in the U.S., sickle cell disease is far from rare on a global scale. The World Health Organization estimated that 7.74 million people were living with the disease in 2021, with 515,000 babies born with it that year alone. Nearly 80% of global cases are concentrated in sub-Saharan Africa, where in some regions as many as 2% of all newborns are affected.
Even within the United States, the frequency varies dramatically by population. Among African American newborns, sickle cell disease occurs in approximately 1 in 360 births. In the District of Columbia, the rate is 1 in 437 births overall. Nationwide, a 20-year analysis of newborn screening found 1 case for every 1,941 births across all populations. So while the total number of affected Americans is relatively small, it is not evenly distributed, and in some communities the disease is a familiar reality rather than a rarity.
Who It Affects in the U.S.
More than 90% of Americans with sickle cell disease are non-Hispanic Black or African American. An estimated 3% to 9% are Hispanic or Latino. The disease is inherited, requiring a copy of the sickle cell gene from each parent. People who inherit just one copy carry the sickle cell trait but typically don’t develop the disease itself.
The concentration of sickle cell disease in specific racial and ethnic groups has shaped both awareness and access to care. Many specialists and comprehensive sickle cell centers are located in urban areas with larger Black populations, leaving patients in rural areas or regions with smaller affected communities at a disadvantage.
The Funding Gap
Sickle cell disease’s rare disease status hasn’t always translated into proportional research investment. A comparison published in JAMA Network Open found that between 2008 and 2018, sickle cell disease and cystic fibrosis received similar total amounts of federal research funding, even though sickle cell disease is three times as prevalent. Per person, the gap was stark: federal funding averaged $812 per person with sickle cell disease compared to $2,807 per person with cystic fibrosis. Foundation funding widened the disparity even further, with cystic fibrosis receiving roughly $7,690 per patient from private foundations versus just $102 per patient for sickle cell disease.
This funding disparity has had real consequences for the pace of treatment development. For decades, only one medication was available for sickle cell disease. Progress has accelerated in recent years, culminating in the landmark 2023 approval of two gene therapies, but the decades of underfunding relative to the disease burden remain a point of frustration for patients and advocates.
What “Rare” Means for Patients
For people living with sickle cell disease, the rare disease label is a double-edged sword. On one hand, it provides regulatory incentives that encourage companies to invest in treatments they might otherwise consider unprofitable. On the other hand, the word “rare” can minimize the disease’s impact in public perception, contributing to less awareness, less philanthropic support, and fewer trained specialists than the condition warrants.
The reality is that sickle cell disease sits in an unusual space. It is rare by the strict legal definition used in the U.S. and Europe, but it is the most common inherited red blood cell disorder in the world and one of the most common genetic diseases overall. Whether you consider it rare depends entirely on where you draw the line, and for the millions of people affected globally, the label feels like a poor fit.